So in other words you think every battle ability is shown before hand? Mind explaining why every other character has Pokemon that do the same thing?
It should be foreshadowed at the minimum. In any case, they don't show it all of the time but when someone criticizes it as bad writing, which it is, then they (the writers and their fans) shouldn't complain when people do so. Every other character has Pokemon that do the same thing because of poor writing. Simple as that. This isn't a special case nor is it the first, the last, or the most egregious. It's just this case that happened in this episode and pointed out in this thread which discusses said episode.
Why does this bother you?
Because it's poor writing and you decided to pursue the issue to get my opinion on the matter.
Characters win against more experienced characters all the time. Drew lost because his Roselia couldn't counter Medicham the way Beautifly could. Roselia can't fly, couldn't immobilize it, its pretty simple really.
I don't have a problem with characters winning against people who are more experienced than they are. That's to be expected in shows like this. I have a problem with the fact that there was nothing showing that May had reached this level as a trainer and that she suddenly gained the skilled required to do so for no reason.
Since when do you lose against someone once and then never beat them again anyway? Its too bad Grace never returned but its not like characters can't win against someone they lose to prior.
This has nothing to do with what we're talking about.
I am well aware of each characters flaws. Seems to me that Rebecca is making a mountain out of a molehill, as if this is the only time in the entire series such an event took place. I guess she must have been oblivious to the 100 other times its happened.
I've probably pointed some of these things out in other threads that are primarily focused on battling. I don't point it out in episodes that don't have battling as a focus to the degree that Pokemon Contests and gym battles do. This just happened to be one of those episodes.