If we will use smth like this:
#minecraft:is_forest
mod will work only if we already spawned in this biome.
In other cases:
[13:27:13] [Server thread/INFO]: [Biome Spawn Point] Finding the nearest '#minecraft:is_forest
minecraft:the_void' biome. This might take a few seconds.
[13:27:13] [Server thread/INFO]: [Biome Spawn Point] Unable to find custom spawn point.
even if #minecraft:is_forest is 64 blocks away.

I haven't used ',' betveen biomes.