McGinn played a handful of games in Philadelphia -- 36 across two seasons, to be exact -- but never really earned a long look at the NHL level.
He's a restricted free agent right now and the Flyers did send him a qualifying offer earlier in the week, and it's likely that McGinn wasn't interested in signing a contract here without a real chance to crack the NHL roster. He's 23 years old -- it'd be silly for him to accept a fate wasting away in the Lehigh Valley.
So Hextall went out and got something for him. That third round pick certainly has some value, and stockpiling draft picks in exchange for players that have little-to-no value to your club is just a savvy move. Hopefully we see more of this, especially since Hextall has expressed a commitment to building this team through the draft.