I understand your train of thought.
Unfortunately, I am not very strong in this matter to draw conclusions based on these quotes or other sources. Whether Kazimir Malevich is the founder or just made a significant contribution is not important to me. I think that as many people as there are opinions.

I used to be very skeptical about his Black Square. For an ordinary person, it's just a black square on a canvas and he does not see any special artistic value in it. This value is created by art historians and philosophers.
As a patent specialist, I see a brilliant solution. Whoever draws any square in the future will always be compared to Malevich's square)
Moreover, they will compare any regular geometric shape.