I’ve found a weird behavior in pcbnew when routing tracks (interactive router). When the net name ends with _P or _N (maybe also +/-), the interactive router picks the trace width and clearance from the DP settings in the netclass, even when not routing a differential pair. Is that the expected behavior? I’d have expected those settings only be chosen when the interactive router is in “DP” mode, but not when routing single traces. The net is not intended as a differential pair, it’s just a crystal where the net names happen to XTAL_P and XTAL_N.
Not a huge problem, but certainly caught me by surprise.
As far as I know this is by design. It allows to work on DP-nets also with the standard route-tool (e.g. for making corrections/changes/whatever reason).
Maybe change your crystal-netnames to XTAL_in/XTAL_out?
Yes, it’s expected as mf_ibfeew says: you may be tuning the position of a single member of a differential pair using the single track router. Right now, KiCad knows what is a differential pair or not using the net name suffixes, so you should not use those suffixes on nets that are not differential pairs (at least, not if you want to configure different DP design rules)