Two plant placement/growth condition bugs (2021.1)

I was happy that 2021.1 introduced the option to select the blocks that a plant can be placed/grow on. But now, using it, it seems to be bugged to the point that made continuing a bugfix on my mod frustratingly impossible. Let me explain:

• First thing I did is that I created a plant, set its plant type to caves, and used the "optional list of blocks" field to specify valid blocks for it. When I went to test it in the client, I couldn't place the plant on any block! Nope, not a single one! 
• Discovering that it didn't work, I then proceeded to delete the blocks in the optional list and decided to use the "additional placing/growth condition" check (procedure) instead. And I kept the caves plant type unchanged. Here's what my procedure looked like: https://i.imgur.com/TKxlEDj.png. The placement worked this time; I was able to only place it on the specified blocks! But whenever I set the plant to generate on a particular biome and my spawnpoint is in that exact same biome (Forest, for example), the console shows an "unable to find spawn biome" warning, which it says is a server error! Then the game just freezes in world creation. No crashes, no responses from the client... nothing but that one warning. Ugh :/

I just wanna know how I can make my plant placeable on the blocks shown in the image, without giving any error. Please, if anyone can help, it would be very much appreciated. Thanks!