Nether Fortress broken bridge structure does not generate anything inside Netherrack

When a Nether Fortress attempts to generate the external broken bridge structure (represented by the ID "NeBEF" in Fortress.dat), and the structure is surrounded by Netherrack, no structure generates inside the bounding box. The fortress simply ends at a wall of Netherrack.

Seed: 2726140590913983575
Go to Nether
Gamemode spectator
Tp to -206 66 171
inside Netherack, no structure
face North, end of bridge can be seen
Tp to -58 66 139
outside Netherrack, structure appears correctly