Golds & Plats can get the exit rows upon booking. Silver elites can only get the seats at the T-24 hr mark, the same as non-elites. My guess is that:
1. Golds/Plats are being upgraded at the 24:01 mark and thus allowing the seats to remain open at the T-24 hr check-in point.
2. If any exit rows remain unbooked, you're getting them before others because you're connecting and can check-in ahead of the 24 hr mark... I presume you're flying out of Tyler, TX from your handle. If you're going Tyler-IAH-XXX, your 24 hr mark is before someone going IAH-XXX, so you can snag the seats before they're even eligible to check-in.

Be cautious... you might have opened up a can of worms with this thread. Many Silvers (myself included, when I was one) want CO to allow Silvers to be able to book the exit rows at the 48 hr mark, or prevent all non-elites from booking the exit rows at all. It's been hashed out on here many times, so lets not turn this thread into that. Maybe this is something that should be raised at DO IV?