I think that actions deserve consequences, either positive or negative, and my now adult children knew that, as does my granddaughter. I never threatened my kids with a consequence that I could not live with, the punishment is also mine, you see. So to answer your question, when on vacation, they knew that if I said that enough was enough, they knew exactly what that meant....any more and the day was done. But that disciple was for them, their lifetime. I don't think parents can suddenly teach their kids to be patient, well mannered and self controlled in a week, so they will not magically turn into those model children that live on Leave It To beaver if they were not taught that from the start.
It is impossible to know what a family's background is from a ten minute encounter, but I will say that parents who simply must have that meal at 'Ohana, even if the ADR they scored is at 9:45 and their kids are used to dinner at 5 are setting themselves and everyone else up for disaster. The parents who just must experience fireworks at CG, and that does not take place until 10PM, but their dinner is at 7:30, so they drag it out....not going to end well. And please, if as a parent you never said "no" don't start now. Little Johnney is not going to understand that you have already spent his college money on your bucket list trip, and every attraction ends up in a gift shop that entices him. Buckle up...it is expensive.
My kids were not angels, and we did have that trip when the were tweens that put me over my edge, but I never set them up to fail, and I think that happens a lot. Not intentionally, but WDW is over stimulation, overwhelming, and exhausting.Under the best circumstances, meltdowns are going to happen, parent will either miss a signal or the child goes from 0 to 60 in 2.2 seconds with no warning...not for them or their parents. But those others.....Yikes!