I think that could be called a medical bypass... If you know you have a medical issue that's gonna take a lot of time to resolve (surgery to fix a chronic injury for example), take the upgrade, fly a few months to set your insurance pay baseline, and then get your medical issue sorted out. Get up off of first-year seniority while recovering at home on CA disability pay instead of wasting a year of high bidding priority while at the top of the FO seniority list.

It's probably almost as good as taking an upgrade then signing up for a couple of years of continuous military service.