Plays on the Abhorrence self-titled ep and Vulgar Necrolatry demo and likely more are being mapped to the Abhorrence/Amorphis split, Not sure if this was an automated mistake or an early manual mapping mix-up. 

LBz link: https://listenbrainz.org/album/6f87e01e-99b0-31fd-bd60-0f0f23af912e/

You can see the comparison on my current week imports from last.fm:
https://listenbrainz.org/user/IAmTheBlackMetal/stats/top-albums/?range=week
https://www.last.fm/user/IAmThBlackMetal/library/albums?date_preset=LAST_7_DAYS

And since those are not static, here is another option for comparison (no listens of the bootleg split vs 607 as of now on LBz):
https://www.last.fm/user/IAmThBlackMetal/library/music/Abhorrence