Question: Why do imaginary number calculations behave differently for exponents up to 100 and above 100?

Answer: They don't.

Explanation: Python is broken, due to the flawed culture in computer science that tends to lecture folks on why things are broken instead of fixing them. One notable exception to this broken culture is https://www.wolframalpha.com/, which just now correctly calculated (0+i)^(10^100) to get the answer of 0.