The worst “latte” I ever had was in Costa. Even thinking about it now makes me shudder. There was absolutely ZERO coffee taste in it. Zip, nowt, b-all. It was either the weakest shot in the history of the planet, or the bozo making it completely forgot to add the shot to the glass at all. It was a cross between watery hot milk and, well, it suggested what dirty dish water probably tastes like.
While I don’t much like the notion of not wiping/rinsing the PF, I’d take that over that Costa bilge any day.
The point about the potential status of the cloth is a good one, too. A concientious barista would change it periodically but unless you are confident they do, that’s probably a much greater hygiene risk that an unwiped PF. Cloths, unless changed periodically, seem like a perfect breeding ground for bacteria, and a post-wiped PF might look clean, but …. ?