I think you are making a lot of assumptions here without any firm basis.
The problem is that there are many permutations of possibilities for all manner of roles for this submarine simply because we don't know its details. Heck most people can't even fully agree on its length or beam.
So if the question is "could a SSGN fit in a 120m length, 12m diameter submarine" -- the answer is yes. That's because there are absolutely permutations of the design with what we see where a credible heavy load of cruise missiles could be accommodated (e.g.: 09V likely has 8x tripack tubes for 24 missiles -- one could easily see 16x tripack tubes for 48 missiles in a 120m length submarine if the torpedo compartment is reduced to shift the command and crew compartments forward).
Alternatively, if the question is "could a 120m length, 12m diameter submarine be any other role which isn't a SSGN" -- the answer is also yes, because there are permutations of the design where a larger missile load isn't viable.
My recommendation is to stop trying to "pin down" what this thing's role is first.
Our job is to be quiet, listen and observe and see if any better photos emerge and then await what the Chinese language grapevine says.
Because as it stands, trying to debate its role where so much of its characteristics are unknown, is just a waste of space and time.
