I tested this a few times with latest version using the following settings:

I:biomeReducer=40
I:endBiomeSize=11
I:treeFrequency=1

https://i.imgur.com/owo8uvR.jpg
https://i.imgur.com/GmBKZn6.jpg

I tweaked the biome size down to 4 and 5 and it wasn't happening, but it was still happening at 10. I didn't have time to test out every value unfortunately, sorry!

I doubt this mod will ever be active. Unless you're willing to continue this mod, then its dead.