That's the thing about Maitland for me, last two or three seasons he's been considered a good squad option or backup player for Saracens and each season has ended up back in the team. I'm also fine with him not wanting to come to squads if he had no chance of playing, at his age he's better off just staying at home and playing for his club under those circumstances, same as Ritchie Gray.
I'm actually a wee bit worried about the centres. It sounds strange, but having lots of players in the same position in form is a situation Townsend has fucked up before. It's almost better to have a couple of guys who are clearly first pick, so he can't overthink it.