Let’s stop the euphemisms.
Facility with the tongue implies one can fellate well (and if the latinate clinical term is too high falutin’, then we’re talking about ‘giving head,’ ‘sucking cock,’ or ‘giving a blow job.’)
Being able to tie a cherry stem into a knot doesn’t seem like a good indication of fellating well anyway, since one needs to use teeth in tying that knot. And just in case one is that naive, let me point out teeth and fellatio don’t mix well.
Peace.