There are little things you learn when your trad that give you a head start with WFP.
Take letterbox runs as one example, it's easy to wade in with WFP and leave the glass wet, you would be long gone before the runs became visible.
I think there are more jobs lost through doing front doors WFP than any other reason. I am not saying you can't do them, but you have to be selective about which ones you do.
Same with slightly open windows left on the catch, some are designed in a way that won't let the rain in, you can carefully WFP the openers above these, but some you can't.
As long as newbie WFP users are careful, and take the time to think about the job, they should be fine.
We had the benefit of good WFP advice from others on this forum, others went for proper training,
but without these or at least a good grounding in trad work, it's very easy to give wfp a bad press.
The guy I watched may have been better employed in the fire service.
If there is any snobbery, it's between those of us that always try and do a first class job, and those that give our profession a bad name. Dai