Unstable meaning it's less supported so more likely to be bugged
Eh, thats quite a lot of bull... First of all that has nothing to do with stability. And "bugged" has nothing to do with the filesystem, that would be a software error. The filesystem works good and theres nothing wrong with it.
Also, in case you didnt know, WBFS is whats most supported by loaders. FAT32 support came quite a while later, and NTFS is still so-so.
There are some drawbacks with wbfs, yes, but theres also plenty of good stuff.