shoes “firm up”?
That seems unlikely on the face of it. It’s worth bearing in mind that there are a couple of different midsole materials used by Hoka, the original one is EVA foam, but around a third softer (from memory) than the grade used by other running shoe brands. Then, a couple of years back, they introduced a more durable, and slightly firmer foam in some models, which is a mix of EVA and rubber, I think. It’s called RMAT.
Also, with ith the ‘firming up’ thing, i think some models have a softer ‘Top Midsole’ layer so I guess what may have happened is that that upper layer softened up to the point where the foot was effectively feeling mostly the firmer main mid-sole, so it may not be quite as unlikely as it sounds…