Potential Info Leak in Required Bosses Mode without Reveal Full Sea Chart

[RecursiveVision]

Playing with Required Bosses Mode (all 6 bosses), currently I have these six markers on the map.

Whenever I get a Fishman to draw a quadrant on the map, during the cutscene, all but two of them fade away.

This glitch can be replicated with any seed. If there's a way to tell which bosses those two markers are pointing to, this could leak information. Even if there isn't, it's still a visual bug.