I think this is standard for United. If they can blame it on ATC/weather they will. I was once on a flight where we were told the delay was UA's fault (can't remember exactly - I think it was due to crew), but then there was a minor weather hiccup and by the time we landed the official reason had switched to "weather" and all those we missed their connections (it was the last flight of the day) were out of luck. I only managed a hotel room based on my 1K status.