I don't know how the chesss.com analysis decides a move is excellent but it may just be that the moves you made either maintained or increased the advantage/score that was evaluated after your opponent's move.
As to inserting a game, the insert dialog doesn't pull from your archive and games have to be entered manually or inserted by pasting the moves/PGN text. Last I knew, that didn't work for mobile correctly (at least not for smaller screens).
Though a feature to pull from the archive would probably be useful.
I am at best an average player but the chess.com computer analysis gave me 10/10 excellent moves for my most recent game. Granted it was a 10 move checkmate and my opponent's moves helped but I didn't think any of my moves were anything above standard.
Does it award excellent for any opening move that isn't known to be bad?
P.s. I would post the game but I can't work out how on my mobile. I have used the insert game icon but can't see where my archived games can be selected on it.