The interesting thing is that if you try to generate that same seed in 1.18.12, the Portal don't get overwritten despite part of the mineshaft being still inside the stronghold.
In the same seed I found another End Portal at -888, -19, -418 (the Closest to Spawn), which it is partially intercepted by an Amethyst Geode, althought is it not destroyed.
The interesting thing is that if you try to generate that same seed in 1.18.12, the Portal don't get overwritten despite part of the mineshaft being still inside the stronghold.