DL (non-union, it must be said) uses verbiage fairly close to cabin manager (I think "flight service leader", typically the F FA on narrowbodies). Not sure if this is a formal thing or just something the FAs agree among themselves.

A thought: a lack of boarding pay effectively makes longhaul flights higher-paying per-all-in-hour, which would lead to more experienced FAs bidding more for those. Boarding pay may have the effect of shifting FAs for whom it's just a job to bids for shorter routes ("at least I can be home most nights"): that could have been part of DL's motivation for boarding pay.