It would be helpful for you to discriminate between what you
can do and what you
should do. If you're saying you
cannot, then the facts contradict that. If you're saying you
should not, then you may be right, at least in the context of majors. Many commuters, however, will be satisfied with any loggable PIC time.
It's important to know the truth before you decide how to use it.
Remember, this is a career-oriented advice-based website.
From what I know of the hiring process, if you have CRJ FO as the most recent experience, never upgraded to captain and have logged a few thousand hours of PIC time in a CRJ because you previously obtained a type rating, you're going to be the topic of some "jovial" conversation.
And most of the airline's human resource departments talk, trust me on this. They don't necessarily officially share data, but believe you me, they're on a first name basis.
I've forwarded the scenario to my "Former Manager of Pilot Selection" that I turn to for the "Hard Questions" section of the main website for the straight poop.
I'll post it when/if he replies.
As much as the FAA cares, you can log whatever you want to log in your book, but when it comes to certification and how HR views it, that's another story entirely.
I wish I kept the old United application to reference their description of "pilot-in-command/aircraft commander" experience, but the airlines look at a very narrow definition of PIC time.
But more or less, if it's going to go on your application and you're not solely responsible for the aircraft and responsible for
signing the release, I wouldn't claim the experience as PIC, legal or not, when applying for an airline.
I know if I was looking across the desk, asking a new applicant questions, I'd say "Ahh, never upgraded to captain at SkyJet, but you've got 2,000 hours of EMB-145 PIC under part 121... So, tell me about your FAA PIC route check during your IOE and what upgrade training at your scheduled carrier was like sir".
That's my advice.