Ok, I think it's clear. So, it's much better and more accurate to say compressed public key and uncompressed public key without the word "master" when there's only one private key.
I feel that the terms "master" private and public key were poorly chosen, because they are not keys. The traditional "master key" is a key that can open a series of locks, and that is not what a "master private key" does. I think more appropriate terms would be "private and public key master" because they are used to create the keys, but it is too late for that now.