I don't think him being an overager is relevant. As a 3rd round pick who only scored 43 in 64 games points in his 3rd CHL season, I doubt skipping his 4th CHL season to play in the AHL was even a consideration. He's not an Anthony Mantha level prospect.
He only got his ELC in March, five months after they cut him from Phantoms camp.
It's relevant if we are talking about one making an NHL roster as a 1st year pro. I don't mean to generalize, but I think it is appropriate in this case- overagers are usually low upside players that take time to develop into NHL players, if they even have that potential. The guys that make the NHL straight out of Junior improve leaps and bounds in their late teens/early 20s. Not a 4th year WHL player that was barely above a PPG, playing with 2 future NHLers. That doesn't mean he can't become Ryan Callahan and be a solid NHLer someday, but it's going to take time. Tbh, I'm starting to buy his potential as a straight line, bottom 6, complimentary piece, but I don't think that is any time soon.
A 3rd round pick isn't exactly a long shot. Frederic Allard went 4 picks before Twarynski and he played in the AHL last year and had success as a defenseman. The Flyers will have to make a decision on Wyatte Wylie next year. If he somehow manages to be a PPG player this year, I think there is a pretty good chance he plays in LHV next year. If he spends another year in the WHL I don't think anybody will be penciling him into 20-21 Flyers lineups.
I'm not arguing that Twarynski should have played in the AHL last year. I'm arguing that I don't think he's realistically an NHL player this year.
And as far as his contract, I haven't gotten clarification on this, but I think there is a quirky rule with overagers that if you sign them before March 1st, you burn a year off of their ELCs. I wouldn't read too much into the signing date.