Yes, in a different construction there would be no problem. And there have been plans since at least 2016 to replace/augment the current construction with somet

Yes, in a different construction there would be no problem. And there have been plans since at least 2016 to replace/augment the current construction with something that uses a master key to derive per-chunk encryption keys; it just never has been implemented. IIRC AES-GCM was kinda low on the list with a preference for just using Chapoly, because Chapoly just works and is also secure on any processor, unlike AES-GCM, which is very nasty to implement without hardware support for the arithmetic over GF(2^128).