Last summer I was riding up Vail pass. Doing a decent job and passing lots of people. There was one person on what looked like a cruiser that I just couldn't make any ground on. It took me a while to figure it out. E-bike.
I think they're explicitly banned on that trail but maybe some are allowed if they're lower power.
It's not a big deal as long as the rider is capable of handling the bike at higher speeds than normal. I see that as a problem with rentals.