Spencer walked back that post a bit when he realized Megill has had reverse splits his whole career. I think the numbers certainly back up that it should have just been Megill as always especially when you take into consideration Ashby hasn't been pitching particularly well lately and he has very little experience closing out games (only 1 traditional save in his career and that was in a 3 run game)
wRC+ vs RHP then vs LHP
Baldwin - 130, 178
Olson - 141, 143
Albies - 101, 120
Harris - 143, 122
Then here are the platoon splits for Megill and Ashby
wOBA vs RHH then LHH
Megill - .298, .190
Ashby - .292, .293