That's when Allen, who has spent the entire time flicking worried looks between all three of them, takes a step forward and interjects, quietly enough that he's not so much interrupting as supplementing, "The older Alma here isn't the one from home, though."

Doesn't mean he's not fundamentally still Alma, but even so, Allen knows some differences need to be pointed out if they're all going to be living together from here on out. It's dangerous to talk about both Almas as though they're the same version. Akuma Alma has made it very clear that he killed Kanda, which Allen knows isn't true for their world (not strictly, anyway). Things can get messy if they forget that ― not that this isn't enough of a mess already.

"Our best guess is he's from an alternate timeline."