You keep talking like the clock is a fundamental element of chess.
It absolutely is fundamental. Do you even play chess?
In chess, the most important thing is seeing ahead as many moves as possible. This requires thinking through several different possibilities.
Perceiving deeply into a game of chess requires time. The more time you have to think, the more time you have to consider future moves and thus make better moves yourself. This is known.
A clock provides a restraint. It restricts your time to think. It keeps you from seeing as deeply into the permutations.
Just like having more rest time makes BG3 easier, so too does having more time to think make chess easier.
It's an obvious comparison anyone should be capable of understanding.