Shulkers Do Not Always Spawn in End Ships

According to the wiki, Shulkers should always spawn inside End Ships.

I have found 2 end ships now, neither of which had Shulkers in them.

The gamemode was creative, difficulty was normal, and there were other Shulkers generating in the end, just not in the end ships.

Example to test:
Seed: 1776534992
Coordinates: 1631, 88, -2860