I'm not sure if this was an intentional design choice or not, but it feels like a bug enough to where I've decided to post it here in the tracker just in case. The Ultra Forest Fallen Leaves block is only able to be placed on dirt-based blocks (dirt, coarse dirt, mycelium, grass block, etc). Its behavior seems to be set similarly to things like tall grass and other vegetation decoration blocks. The thing about fallen leaves is that they fall onto whatever surface is beneath the origin point of the leaves without discrimination, so, while this may make sense for things growing directly out from the soil, this does not make sense for a pile of fallen leaves. This placement behavior unfortunately severely impacts the use case for an otherwise very useful detailing/clutter block.

Hi there!

We've recently released a new version (9.1.4) with a lot of fixes! Please re-test your issue, and if it still occurs, please make a new ticket with relevant /battlelog, latest, and debug logs.

Thank you!