Originally posted by Sono:

there hasnt really been much in the way of world generation changes, you just got a really weird quirk in this seed. This has always been able to happen, getting a literal dirt patch as a separate biome. Look on the bright side, super easy troll hide, eyes and resin!

ditto this. I have one map where there's a troll cave within sight of the spawn but no actual black forest. my modded map has a sliver of swamp that is just 4 trees a bit off shore. it spawns 3 mobs that are easily avoided but it is closer to the spawn than usual. Either cope with a map or get another