End Portal can get overridden by other structures

Portal room (more importantly, end portal blocks) can get overridden by other structures such as mineshafts, ancient cities, and also the new trial chambers.

Step to Reproduce:
Load up a world with the seed given and go to the coordinates.

Trial Chambers Overrides Stronghold:
Seed: 940028760242419482
Coordinates: 1443 -17 -1505

Ancient City Overrides Stronghold:
Seed: -3307142256062781398
Coordinates: 786 -44 809

Expected Result:
Stronghold would replace the structure, rather than the structure replacing the stronghold

Observed Result:
The stronghold (and the end portal blocks) get replaced by said structure and you can't enter the end.