Their minds are just mostly subconscious. Not having access to concious sensory perceptions just pushes one towards analytical thought. They can reason effectively, while avoiding bias, by lacking those sensory processes. I'm willing to venture a guess only a true aphantasiac (no concious experience, even of time) has access to objective reality. When you don't have all those distractions going on up there a more accurate view of the world results.

I'm going to venture a guess a ton of important mathematicians and logicians have minds along this line. It let's you get in the proper head space for conceptualizing non-visual dimensions. Now, that the term aphantasia*; but, differently
exists we can start moving towards a definition of conciousness, and learn how to intentionally alter our concious states.

Now, the big question resulting from this discovery goes, like so. The STEM field has a disproportionate amount of aphantasiacs functioning at an extremely high level. There are literally top researchers and professionals in STEM with the condition. Some of the work actually becomes easier to conceptualize, as a result. So, they designed the modern conception of the computer based on how they believe humans think. Is conciousness computation? Are computers concious in some meaningful sense of the word? Is it possible to alter the concious state so everyone could experience all possible mental states?

Aldus Huxley claimed to have aphantasia, until ingesting large quantities of mescaline, and having a vision trip. Sounds like there might be some truth to the stoned ape theory. Maybe, only a P-zombie is capable of completely rational thought, since no hallucinatory elements get added to the experience?

I'm not an expert on Christian theology, by any means, but aphantasia might be a direct assault against the foundations of their beliefs. I believe there is some Bible line about God putting visual thoughts in heads that is a theological crux for the argument of the existence of God. Either 20% of STEM are irredeemable sinners, or the theology is wrong. Take that to mean what you will.

* P-zombie has too many negative connotations to it, considering that they do philosophize, and it leads well intentioned thinkers astray. But, it is different from how someone who believes p-zombies exist conceptualize philosophy; however, they can still understand continental philosophers, such as the existentialists, by approaching the problem from the angle of time. Heidegger is extremely visual, but at the end of Being and Time he realizes it is literally possible to approach Being from the position of time and space, both must must exist where the other exists. It is a pre-condition for being. They speak of moving through their surroundings mentally non-visually. It is extremely difficult to describe without referring to mystical concepts such as sight without vision. They literally externalize a portion of their mind to the world, and realize their own internal states through listening to monologues, and engaging in dialogues. Which is why Dennet developed the Heterophenomenological model.

I'd go a step even further for the congenitally blind man. He might have an accurate conceptualization of blue, but he will not be aware his mind is seeing blue because he lacks the sense apparatus for experiencing blueness in the world.

If congenital blindness caused by malfunctioning eyes and not the brain can be cured late in life, and the man mentions, "oh, blue looks just how I had thought." We would have to say he was experiencing blue all along; but, through lacking a mental or physical sense (thinking of biology in terms of hardware and virtualization helps so much with this) his experience contains an unsharable quasi-privacy, in his native tongue, which might be expressable in another language or through the invention of new languages capable of capturing newly discovered private experiences succinctly for others.

You're unlikely to get any responses from old posters in this thread, considering it took place 3 years ago.

Philosophers talk about whether p-zombies are metaphysically possible, but what a priori grounds do we have for ruling out the possibility that they're actual? — The Great Whatever

The a priori ground is our assumed metaphysics. P-zombies is completely a derivative problem of mind-body dualism:

Chalmers (The Conscious Mind, Oxford Unversity Press, Oxford 1996) has argued for a form of property dualism on the basis of the concept of a zombie (which is physically identical to normals), and the concept of the inverted spectrum. He asserts that these concepts show that the facts about consciousness, such as experience or qualia, are really further facts about our world, over and above the physical facts. — 'Human Zombies are Metaphysically Impossible' – William Robert Webster

If you are a physicalist, traditionally, you will automatically reject the idea of zombies — there are only physical facts and two individuals with the same physical facts will both have consciousness or not. If you are a dualist, you may reject the idea or not depending on your flavour of dualism. If you are an idealist, I don't know, I haven't dropped acid yet.
Each will come with its own set of its issues (which the SEP article redundantly covers in every derivative problem), and the debate has raged on since Antiquity — pick your poison and accept you can't solve the conundrum.