But, principal, staff, lead, and senior are all pretty much the same tech skill level.

I don't really understand that... you think someone at the level of a distinguished engineer, maybe something like a Turing Award winner or someone who has invented fundamental concepts in the field, is 'pretty much the same tech skill level' as someone just promoted from mid-level developer doing routine development work?

I also don't see why it's 'title inflation' to recognise the difference between those two?