Can't spawn phantom (final boss) in old map Adventures in Khundalan

Partner Rank: 2

Verification builds: 1.17.1101, 1.17.3024
Regression builds: 1.17.50

Summary: In the map Adventures of Khundalan, the game now thinks summoning a phantom is a syntax error. The final boss is a phantom, so it never spawns.

Impact: Impossible to finish ending of map. This is an old and unpopular map though.

Repro Steps:

1. Download and open Adventures in Khundalan from the marketplace.
2. Enable cheats and /summon phantom

Expected Results: Final bird boss is spawned

Observed Results: Syntax error. Also a content log warning tells you that the boss spawn function failed to load.

Screenshots/Videos attached: No