I think it would be a good standard practice if on group ride events the initial pace was well below advertised, slowly working up to avg. That would give those slower riders, or folks who joined just-in-time to get their legs ready for the harder effort. Because once you’re dropped you’re cooked, even if you’re putting out more watts than the main group (because of drafting). It’s okay to get dropped later because you’re slower, but if I’m 5 minutes kind of sucks
That is up to the Ride leader. But I do agree an easy start is the way to do it. In my rides we start nice and easy then work it up.