...wait didnt that already happen ? I know lot of people pulled this gacha.
It happened twice. I don't remember who got a random Shiro-chan and then the Maid Cowslip reward and I got a random Maid Cowslip and the Cowslip reward.
If you do the 55 rolls, you will have the featured 6* no matter what you get in you rolls before. it's just a "paid 250 FG for the 6* and get 5 rolls as bonus".