Cat, muzzles will also deflate after a course of some meds including cortizone. Yes they more often than not do return to normal, sometimes it takes a week, sometimes it can take up to a year!
In Noah's case, he had a really big meaty mouth until he had a course of injections for demodex, and it deflated somewhat. Actually SPR NSW & Peipod were both surprised when I sent them pics of how lean his muzzle is now. Aren't they the funniest creatures (pei that is not SPR NSW & Pei pod) ROFL