For the dress issue, it really just depends on the context and your relationship with the person. If it's your -friend- who you actually know makes custom dresses as a hobby, why would they be upset at a (genuine) compliment? My friends who pay attention to clothes and I give out (genuine) compliments to each other all the time. With a stranger I don't do that unless it's like something that truly stands out. I've been genuinely complimented on my coats and blazers by random strangers numerous times and I think nothing of it. But social environments like bars and cafes are quite different from contexts like office environments, particularly male-dominated workplaces.
I don't know the exact reasoning about the "ethical workplace" training, but I imagine it's a blanket thing since some people just don't know how to give compliments without being creepy about it, or just use it as a proxy to hit on the person. Of course companies large enough for ethical trainings would want to play things as safe as possible. Idiots ruin things for everyone else.
Anyway, I find it hard to believe anyone would take offense at something like "hey, did you make that dress? That's awesome!". But this is also why working at a large corp is probably my least favorite option when selecting a job.
"Males would get very direct, sometimes harsh, and detailed negative feedback, whilst women would get the far less usable vague sugar-coated version of it."
This is definitely an issue and I don't really know how to deal with it other than not hiring people who would take offense at something like honest feedback. That is more of a company-level cultural issue where people are afraid to give honest feedback lest they be accused by an idiot of being <X-ist>. I don't think that culture would develop if they had higherups who they could trust to fairly evaluate the situation. Higherups who are not afraid to go "yeah, no, that's not being <X-ist>, that's just the same level of feedback everyone else gets" if that's truly the case... or higherups who reliably can go "yeah, there seems to be a discrepancy here based on gender and we should take appropriate measures".
...this is a lot of words to basically agree that sometimes edgecases require some additional pondering. Context is very important, and knowing who you're dealing with is also very important. None of this matters if you're dealing with people who assume everything is done in bad faith and you're out to get them, etc. Life is short so just say "alright", and move on. Now, if multiple people start saying similar things... then maybe it's time to do some self-reflection.