Just checked with my daughters Jolla (3.0.2.8 Oulanka), and had only about 2M. Apparently for each SSID seen (not necessarily connected) 3 files are stored (history.home.{day,hour,month}, but they take 3*24 bytes (with btfrs maybe 1M

I suppose you can safely delete the directories which don't contain a "settings" file in it (where e.g. the PSK password is stored).