Oh sorry - basically just a github ticket to an explanation about the .config folder. Pi doesn't respect XDG_BASE_DIR specification, and even if you use the env var it combines cache and config.
The ticket is closed and this will not be changed, period.
From what I understood in the ticket ( I haven't confirmed independently) it's the later. You can set an environment variable to move the .pi directory ( into your XDG Config dir) but it's both the cache and config combined.