I've gotten 2 SSRs in a single pull as well, so what? It happens once in a blue moon.
And of course nothing is guaranteed on DMM Gacha either. But the difference is, it's FAR more likely to happen there. If you save up for something unknown in the future for six months there? You have a fair chance to get it. Not 100%, not by a long shot, but probably more than a coinflip.
Meanwhile in Nutaku, if you save up your Jewels for over a year, chances are pretty much none that you find what you're looking for. That's how bad Nutaku "rate up" for Jewels is.
On a side note, the recent popularity vote Gachas did claim to have 20x rate up even for Jewels. I don't know if that's true, but even if it was, it doesn't seem like it's going to be the new norm. This would be a big game changer for Nutaku players thanks to our ability to see one year into the future, but until that actually happens...