The general rule is that the larger the company or project, the more strict the safety regulations (or safety B.S., depending on your point of view.)

I've seen earthmoving contractors that required hard hats INSIDE the cabs of scrapers. For those of you outside the business, Cat scraper cabs are strong enough to withstand another scraper being dropped on them without being crushed. Thus, this rule serves no purpose whatsoever. Most do require long pants, and when I was in that business, I didn't argue. It made sense. Some I worked for allowed shorts and never issued hard hats. Same exact kind of work.

As far as your situation is concerned, I have a hard time believing loose wiring is a problem when a job is in the plumbing phase, since electricians usually follow the plumbers. Wearing pants rather than a kilt is unlikely to protect you from loose wiring anyhow.

But, in this litigious age, you would be well served to check with OSHA and the G.C. Should anything ever happen to you, regardless if kilts are to blame, the G.C.'s insurance company may deny claims. That's what insurance companies do - deny claims for any possible glimmer of reason or excuse. I can't blame a contractor for wanting to cover his behind.