This is an Aether II issue. Their leaf blocks extend net.minecraft.block.Block and not net.minecraft.block.BlockLeaves. All of the magic happens in BlockLeaves, so if their leaf blocks don't extend this class then they will never be passable with PassableLeaves.

Reference: https://git.gildedgames.com/GildedGames/Aether-II/blob/dev/src/main/java/com/gildedgames/aether/common/blocks/natural/BlockAetherLeaves.java

CC: @jellysquid3 @kingbdogz

I've opened an issue on our issue tracker here regarding it.

This has been closed on the Aether II tracker, so closing here.