Ah! That's interesting. So far I've checked the settings in LR and they all seem to return after putting the crs back.

Are there any significant tags one should know about? In my tests I've usually adjusted Whitebalance, contrast or set to greyscale so that I have some obvious effects to view.
I didn't think to check the whole range of settings.

It's doubtful I'd ever want to do individual tags within crs, most people I'd imagine would just want to be able to keep their current LR adjustments intact.