Is the Abbots Bromley Horn Dance - Morris?
They don't say it is.
The Horns make it somewhat apart from the genre, that and its uniqueness. And more so than, say, "Molly".

The notion that Morris evolved from Moorish/Morresque is well documented. And moved down-market as fashion inevitably does. But it is tempting to imagine that those that already were doing dancing would incorporate moves and flourishes to mimic what was only able to be glimpsed at. Inevitably there would have been traditionalist who would cling to there own style and have no truck with modern fads. Maybe that is what happened to the Horn Dance.

People were no different then, eg we have arch traditionalist and we have avant gaurde Morris danced in: biker gear, Miss Piggy & Kermet, gangster costumes and even mixed in with body popping on stage. And I hear tell of women dancing morris (whatever next?).