We can "run out of" small chunks. After we've switched to allocating medium sized chunks and unloaded a class loader there may be lots of medium sized chunks and only a few small ones. If we start allocating a lot of class loaders after that we can end up expanding metaspace memory instead of picking a medium chunk for new class loaders.
This may will artificially inflate the amount of memory needed for metaspace.

Maybe we could split a medium chunk into small chunks if we are worried about space waste when giving a medium chunk to a newly allocated class loader.

I=M (Uses more native memory than needed)
L=M (Moderately common)
W=M (Increasing amount of memory / reducing amount of classes not always an option)