"when you integrate a function you find the accumulation of its rate of change" is simply wrong. You find the accumulation of the function itself, not its deltas.

GPT is confusing the fundamental theorem of calculus with the meaning of integration.

ETA: what makes LLMs so worrying is that I know calculus quite well, and I think GPT-4 is dumber than a mouse, yet I still felt gaslit by GPT-3.5's wrong answer! I had to make a mental picture to make sure I wasn't contradicting the Mighty Talking Robot. This technology is poison.