Nobody views it as a real chashash otherwise you wouldtn eat it the last day.
What do you mean “real”? Assur meikar hadin? Of course not. A chashash worthy of being machmir on? Perhaps, and the last day being d’rabbonon, is not an arbitrary chilluk.
As for keilim a year later the bleios of gebrokts/ “chashah cometz” dont magically disapear
That’s not so pashut; obviously for most issurim we don’t assume 12 months helps, but for some cases we do, so some are meikil for gebrokts which is merely a chashash.