Ok, I did my 55-pull to check the science that is this new mechanic.
As for the results, I can say it can be a good deal, but only if you really want the featured 6*.
Every roll I had was a gold pot, though I only got two new golds out of it, excluding the event girls.
As for the event girls, I rolled Spring Starflower twice and Oregano 7 times (which was just enough to fully unlock her by the way).
I was hoping for more diversity with those increased rates, but the priority kinda worked outside my favor here.
Personally, I won't be aiming for the 55-pull anymore, unless I really take a liking to the featured rainbow.

As a sidenote for those who have not tried it - the 6* is not included in any of the draws and is simply awarded the same way as rainbow crystals and rainbow coins after the draw.
After the 55th pull, the gacha stays as it was and the counter on it resets back to 55.