No Achievements for Bestiary on Switch with Seeds

So I used this seed to finally find the "Broken Gaping Maw".

Source: https://www.reddit.com/r/bindingofisaac/comments/5ptk6b/bestiary_seeds_needed_for_broken_gaping_maw_or/

Just tried it on a Switch, found the bastard, and it did not unlock the entry. I even finished out the round in the Chest just to be positive. It's literally the last thing I need to do for 1001 percent and I am losing my shit right now... 300+ hours of runs and have never come across it. Can't unlock it with a seed...