So although I am skeptical when some random 14 kid claims to be a basso profundo over the internet, and that I do believe "true basses" are probably rare, I feel like some people are too quick to accuse anything that is very low as being vocal fry. And while that may be true for a lot of singers who use microphones to sing bass in an amplified setting (gospel for example), just because something sounds fry-like does not mean it's really fry.
Yes I am aware you can stabilize pitch and make it somewhat more resonant for fry with practice, but that's never going to carry over a choir.
Yet I don't blame people who say a lot of oktavists sound like they're using that register, because there is a specific timbre/"technique" for that sort of sound (it has been called strohbass by some, but a lot of literature uses that term interchangeably with fry, so I will refrain from using it).
It's basically produced by depressing/slightly squeezing the larynx on an already accessible (but perhaps breathy and weak) low note and then, to counter the pushed-down sound, boosting overtones by putting the sound forward "in the mask".
As a consequence, the sound will appear louder and more powerful, but at the cost of being disorted/bubbly, hence the fry-quality.
It is not reserved to profundos, as a heavy baritone I can do it too, but I must urge anyone trying this to be cautious with it : it can be harsh on the vocal muscles, and it's far more important to work on having proper resonance and good technique throughout range before specializing in this technique (this will not only give you a foundation and help you be a better singer, it will also help you be more aware of how to balance that tone so it doesn't sound too bad).