If i understood you right, your question is:
Why ZenFone Max Pro M1 doesn't support 5 GHz Wi-Fi and could it be fixed?
Answer is simple as question:
Wi-Fi module of M1 don't support 5 GHz range, it means that phone can't "see" networks in this frequency range. Therefore, there is no way to implement 5 GHz Wi-Fi support through software update.
Hope my answer helped you 😃