I haven't heard anything about not using enough rounds, so it's possible that my information is just out of date. My understanding is that AES-128 was chosen to

I haven't heard anything about not using enough rounds, so it's possible that my information is just out of date. My understanding is that AES-128 was chosen to be resistant against classical attacks, and AES-256 was chosen to achieve the same level of security as AES-128 against attacks that incorporate quantum computers and Grover's algorithm.