I think that it's possible his Latin has improved over the years (likewise as some of the Latin Pro specialists have improved in Ballroom), but Anton still isn't that great in Latin if you were to compare him to the other male Pros.
I do wonder if having not so great celebs in the past has almost been a weird blessing for him and allowed him to get away with not having to push himself too far in creating good Latin roudtines on account of the celebs ability not needing it so much. If fiona takes to Latin (better than his previous celebs) then I hope Anton pulls his finger out and puts his best Latin shoes on for her so that she won't be underforming just because he himself as natural at it himself (which no doubt, as a porfessiona dancer, l I'm sure Anton will do to make sure she gets taught at the right standard). I don't blame Anton for using comic tactics with the likes of Widdy and Nancy (as he did what they could do, and tried to make it funny on top), but I don't really see Fiona wanting to be given a clown routine so much. Maybe a fun routine, but not resorting to be flung and dragged around the floor because they couldn't rely on actual steps to get them through a routine.