I disagree.
"Captain select" apparently means you're either selected for upgrade or are in upgrade. I've never heard that term before. You're either a captain, or you're not. Unless you are fully certified to go take the airplane without supervision (eg, completed OE and line check done), then you may be wearing captain bars, but you're not a captain in that aircraft. Whatever you did before doesn't matter much.
Upgrade is not a function of seniority. You can't upgrade until your seniority allows it, but seniority is not a guarantee of an upgrade, nor is it automatic, and it's not a "gimme."
We all know a captain or two that is no shining beacon, and have perhaps wondered how someone managed to upgrade. I've known a few, several of which wound up being fired, downgraded, or driven away. I've known some who didn't make it through upgrade, and quite a few who were wise enough not to bite the worm the moment their seniority first allowed them to get a class.
Being selected for upgrade does'nt mean a lot. Different operators do it differently. I've been at some places where upgrade meant multiple recommendations, review boards, etc, and other places where a warm body got pulled and either sunk or managed to swim. I've been places where captains were direct entry, but in such cases not all were suited and some didn't make it through class, some didn't survive long on the line, and so on. There are no guarantees of upgrade. Only opportunities. One rises to the moment, or one does not.
Certainly experience as a captain is a benefit to one's resume. It does represent the trust of the employer, having met a particular standard, and that one continues to meet that standard. Likewise, experience as a check airman represents a standard and is worthwhile citing on a resume. Having been offered such a position doesn't mean a lot. Completing the training program and being placed online means more, and time in that position also means something.
Each of my upgrades have involved multiple recommendations (which I have never solicited, and which I will not do), selection committees, review boards, etc; getting the offer was not a shoe-in, and neither was the upgrade (the exit oral on the 747 was 8+ hours with two check airmen, and we covered everything). Regardless of where you work, being offered an upgrade slot is significant, but not on a resume. Being captain is significant on a resume. Get the qualification, get some experience once you get the qualification. Being a captain is as much about managing the cockpit as it is flying airplanes, and that's not something you're versed in simply as a function of completing the program or wearing an extra stripe. Get some experience doing that job. That brass ring with the next biggest and greatest, doesn't have to be tomorrow.