In real life any type of race either has all participants starting at the same time or they are starting in intervals with time adjustments. The mythic progression race works the same way to sane people.
You are most welcome to keep deluding yourself though since the US players appear to need every single advantage they can get.
I know you just want to rub your weiner to the US having those WF for those easy bosses, but that not how real racing works. If Guild 1 goes in as soon as the raid unlocks and take 1 hour to kill the first boss, rhen Guild 2 goes in when their raid unlocks and take 15 minutes, then Guild 2 should have the prestige, since they killed it in less time from when they could enter the race.
There's a reason track runners that run 200m and greater start in a staggered formation in their lanes. It's so they run the same distance and are treated equally. In your world they all start at the same line, and the poor souls on the outside have to run and perform much harder just to cross the finish line before those on the inside lanes.
SB actually raids daytime but kills bosses after 19:30 so the mmo-champion police don't find out.
Don't tell anyone.