The problem with that theory is these guys don't go elsewhere and shine, like say Verhaeghe who got jacked around by Toronto and TB.
Giroux was 1C, Couts and B Schenn were basically competing for 2C, Couts beat him out in 2015-16.
Couts took off when G was moved to LW and paired with him.
Laughton was sent to AHL b/c he couldn't play defense, came back improved but has always been an awkward fit at center, better LW but Flyers have had a hole at center for over a decade (moving G to LW improved 1st line but left a gap, and Patrick flaming out left a chasm).
NAK has always been a 4RW at every stop in his career.
Kase wasn't even a good AHL player. His 2nd AHL season 51g 7-12 19 at ES, and he couldn't stay healthy. Injuries also derailed Laczynski (top college scorer) and Allison.
Hagg should have been a top defensive defenseman, but seemed to lack the instincts, never was good offensively, even at the AHL level.
Sanheim didn't knock anyone's socks off offensively in his first AHL season, 76g 9-15 24 at ES. Next season, 2017-18, at 21, was too good for AHL but not ready for prime time. Hagg replaced him in the playoffs b/c of bad play. The following season became a fixture in the lineup.
Frost's first AHL season in 2019-20, 41g 11-8 19 at ES. Played 20 games in the NHL, 1-5 6 at ES. [Twarynski was a LW, he didn't keep Frost off the roster.] Missed a season. Next season much better at LHV, promoted to NHL, but 55g 4-10 14 at ES. After a good 2022-23, regressed a bit last year despite PT with TK, Tippett and Farabee. Frost's problem is Frost, hasn't learned to play up to his raw skill level.
Brink struggled at the NHL level last season, needs to get a little quicker, little stronger and adjust to smaller windows. Showed he was too good for AHL, but not quite NHL ready.
xGFrel -6.07, HDCFrel - 7.88. 1.59 pp/60.
Note that a lot of prospects needed a year or two to adjust to NHL play.
The progression tends to be go to the AHL, show you're too good for that league, get promoted, struggle as a rookie, step up your game your 2nd year in the league.
Players who are good defensively play earlier, not because of some prejudice, but b/c you can fit them in the bottom six and let them grow into bigger roles (Couts at 18). Cates, Foerster.
Offense first players who haven't mastered defensive fundamentals are bad fits in the bottom six and are rarely good enough offensively to make the top six as rookies, so they're more likely to be marinated. Frost, Brink.
This isn't a "Flyers thing," look around the league and you see the same pattern, especially teams that are good at developing prospects. Pens marinated prospects on a regular basis, which is why their AHL franchise is consistently competitive.