While SM is the most blatant case, this has basically been the deal with *all* of Ash's outfits since DP:
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Ever wondered why the male PCs never appear on the show outside of minor cameos? Because Ash is literally filling in their role, hence him wearing their clothes.
(As an aside, this is likely also why the male PCs themselves have looked very boring and samey since Gen 4. They're basically being designed to be new outfits for Ash, so they all have to have Ash's color scheme and be at least somewhat based on Red, if not an outright clone of him.)
It is definitely sad that the anime is to blame for male protagonist designs getting worse every generation. AG was probably the only truly unique Ash outfit when you look at it, since it was a hoodie and not a long-sleeved coat.