a formal schism would require one party to excommunicate the other
John Lackland was excommunicated in OTL, but patched things up four years later. If ITTL he didn't and claimed headship of the Church of England, but as a middleman between the Pope and the English clergy rather than doing it Henry VIII style, how implausible would it be for England and Rome to drift apart gradually and without much fanfare to the point that, by the time the actual schism happened, the Pope's first reaction to the news would be akin to a rather bland "Well, that was bound to happen sooner or later, I'm just surprised the situation boiled over due to English king's marital problems"?