There are always different opinions about players and opinions vary. Rosewall had a great backhand, arguably the greatest ever but of course not everyone who played him thought he had the greatest backhand they ever face although it often seemed that way. Trabert had a fabulous backhand and probably one of the all time greatest also but I've never seen it argued as the greatest backhand ever as Rosewall's or Budge's was.
Arthur Ashe's ranked Rosewall's backhand the best along with Rod Laver.
If Hoad said that about Trabert's backhand, that's fine but I'm sure Rosewall's backhand was very important in so many of Rosewall's victories over Hoad.