1) As long as this is not clearly spelled out in the TOS _and_ you trust the company (again?) to keep it up, without changing it back in the future, you could now go with a fake name. You'd invest in a social network that asked for IDs in the past to get access to the data you created on their platform and wouldn't be able to provide an ID to get to the data for this account, even if you'd wanted to.
2) The criteria are still unclear. At what point does it stop looking like my real name? Should I play safe and go with John Smith? Is that maybe already very suspicious and probably not my name, period? How creative can I get choosing the required fake name without triggering this alarm that would block my profile?
3) This defeats the whole purpose of the policy in the first place. A "real name policy" (call it community guidelines or whatever, if you like) only makes sense if you verify the names. Otherwise it is a 'no funny names' (what's considered funny?) or 'no offensive names' (recently mentioned on Raymond Chen's blog: Microsoft changed the internal abbreviation of customer from 'cu' to 'cx', because the former is an offensive word in Portuguese.. Where's the limit?) policy.
For all intents and purposes: There is _zero_ progress here, and it really took them a loooong time to add an additional simple field to their data model, plus two options on how you want to render it on your profile.
And - nicknames are only useful for searching/lookups. I can put them up in my 'about' section. Google is a _search company_. I doubt that it was impossible to find people that wrote 'Hey, this is MikeMasterOfGuitarHero' anywhere near their profile by knowing that particular name. But being _only_ available using a name that you pick yourself - that's still missing.