Adamsmashem Yes, porting is the process in which you transfer your number from one carrier to another. As far as privacy goes, I'm not sure what your goal of privacy is, anything that's not zero knowledge end-to-end encrypted is unsecure communication, as in your messages can be intercepted. After doing some reading, it looks like googlefi may be encrypted? or only just for calls? I'm not entirely sure, eitherway you still have to trust Google that it is properly implemented and that google does not have a key to access the communications.
If it's from your parents, i'm going to assume that the googlefi numbers were not purchased anonymously and therefore your identity is tied to them, so that's another -1 point for gryffindor.
My question woud be, how does having an active google account tied to the phone impact your privacy? And honestly i'm not entirely sure. Someone here more knowledgable than me particularly regarding how google accounts are effected with GOS sandboxed environment can answer. My understanding is that google hardware fingerprints, but GOS may have implementations to minimize this. If not, you'll still have some increased restrictiveness over other less secure phone OS's due to GOS google sandboxing. Here is the source for information pertaining to sandboxed google play: https://grapheneos.org/usage#sandboxed-google-play
Without knowing what your concern is, just being concerned about "privacy" is too broad of a question.
Some information you might find of value: https://ssd.eff.org/