Yep. It's fantasy. Nothing more. Nothing less.
Why not Electroluxes or mops?
Dunno. Ask the animators. Is an Electrolux less evil than a broom? I know they cost more...
Fantasy of "what"?!? It's not like a movie of geometric shapes wafting about at random. It's animated brooms. "Everybody knows" witches ride these. (Why didn't Harry ride a vacuum cleaner?) At the very least the church ought to give a warning about the connotation.