I’ve seen this at funerals. People often seem to think it’s necessary to wear black at funerals, and if the only thing they have that is black is a mini skirt they might otherwise wear clubbing, they wear that.
Weirdly, recently at a funeral, there was a man wearing quite a loud checked suit. It was bizarre. He obviously thought it necessary to wear a suit, and that was all he had.
Usually, people wear something sober, in a dark colour. Occasionally, there is a request to wear something within a particular colour scheme. Once, we were asked to wear colour, because that is what the dead person wanted.
Re the short white dress, I wouldn’t wear it to a wedding where there was a bride (or 2) even though it’s not very bride-like. Anything white would be inappropriate (as in, it might upset the bride/s, so I just wouldn’t do it). At a wedding between 2 men, I would think it was fine.