Seems they wanted to restrict the cheap +1 attribute boost, that was so prevalent in the surgelings I saw.
Then wouldn't it be easier to just nerf, or even completely do away with, the quality? It
was poorly designed in SR4, because it was
blatantly superior to exceptional Attribute. First, because it didn't just raise the maximum, but actually raised the Attribute, for the same cost. Secondly, because it wasn't actually the same cost after all. Gettiing SURGE II meant you got it for 10 BP instead of 20, although technically it was a 20-point quality balanced out by 10 points' worth of negative qualities. Time to give yourself some cool anime-style crayola hair and funky eyes. Or if you don't even want to
look like a changeling, get a moderate allergy to silver, or nano-intolerance and weak immune system. Or get astral hazing, one of the other overpowered options, as your 10-pointer "flaw".
So yeah, the good thing is that glamour and the aforementioned astral hazing both got powered down, and while the metagenetic improvement is still blatantly superior, it still gets nerfed overall because it is part of a less-than-optimal package deal. In SR4, 15 points got you 30 points of positives balanced out by 15 points of negatives. But they raised it to 30
and doubled the amount of flaws. You are essentially paying 30 points to be a changeling, points that come out of your limited supply of starting Karma (or, if you are using Point Buy, your limited supply of Karma, period). For the cost of a mystic adept getting 6 power points, you get to be a freak - one with lots of quantifiable disadvantages, on top of being very distinctive in a vocation where that is a big disadvantage.
Personally, I don't like the random options. Both because they confuse the original intent of the I, II, and III designations, originally denoting the level of severity of the SURGE, and because I don't believe random rolls have any place in character creation. I think SURGE III got a bit over-nerfed, too. Sometimes I think they worry a bit
too much about "fixing" everything that was a good deal in SR4, and wind up with options that are so sub-optimal that no one takes them.