When it comes to Chrom's Aether, it is different from Ike's. Jumping with the sword, more emphasis on horizontal movement, etc.
Honestly though, who cares? If we already have Lucina as a clone of Marth even though she has no way of being able to know how to fight like Marth/the Parallel Falchion being downsized by half to fit the original Falchion, I don't see how Chrom doing Ike's Aether and not his own to fit into an Echo is a problem. As I've said before, lots of Awakening is an amalgamation of FE mechanics, concepts, names, etc. mixed into one, so Chrom's "Aether" could very well be based on Ike's Aether already by sharing the same name and general movement/animation.