Is it less genuine than (say) Rose Queens, drum majorettes or 'fluffy Morris'? If so, why?

Why? Because these things happen as unselfconscious folkloric practise. Simply put they are not Folk because they are not recreations by a separate class of (superior) people who, in any case, regarded them (or at least their immediate precedents) as being '...degenerate...by...extreme popularity...' (see caption for picture 3 on p 82 of The Imagined Village). Fluffy Morris is thus real in a way Border Morris never can be; the latter is folk posturing operating at several very significant social, cultural, anthropological and historic removes from its prototype, whereas the former is the Real Thing : a 100% genuine living working-class community tradition practised by 100% genuine working-class people living 100% genuine working-class lives in the Real World and, therefore, about as far from the faux aestheticism of revivalist hobbyism as you can get.

Even if there were non-racist reasons for the traditional dancers of the 19th century to have blacked up, for a morris-person to do so today is akin to the paedophile citing the AOC laws pre 1875 to justify their desire to have sex with 12-year-olds.

The past, as they say, is another country. Best we leave it where it belongs.