Technically Phos' face has not changed, it's just an exaggerated range of expressions. It would lose a bit of impact if Phos' face was drawn in the same way before and after winter.
The problem is that in the manga Phos' face can instantly switch back to GenkiPhos because the artstyle allows for it, and we, as readers, are aware that Phos' face only currently is drawn like that because of his "dead inside" expression.
Phos' face switches around like crazy in the manga, it's not only back to GenkiPhos, sometimes his eyes become narrow as fuck, and other times they look tareme instead of tsurime.
But in the anime they have fixed models that don't change regularly, so we get the impression that Phos' face has literally been resculpted.
Also, in the anime, Phos jaws become slimmer, on top of his eyes changing, incidentally using the same face shape model as Antarc, who also had slimmer jaws than the other gems.
If we were to get the Genki moments in the anime it would look really out of place because of the fixed models, so probably the most we can hope for is that his irises are enlargened like they sometimes were in the anime post winter.