Can I keep feeding 1.3yrs corgi puppy food?

long question short :

He's only interested in Royal Canin Medium Puppy, and his stools have been great on it. We've tried Royal Canin Corgi Adult and Medium Adult, but the kibble is too large. We also tried Hill's Small Bites, but he doesn't seem to like it(not smell as good as RC). If I continue feeding him Royal Canin Medium Puppy and simply adjust the amount to meet his calorie needs, are there any downsides?

thanks folks