It's 900p, but with some magic sprinkles to make it 900p (or 1080p in the PS4's case.)
Pure graphical prowess isn't the game's strong suite. Tactical gameplay by being able to chip away at walls/ceilings/floors for example is the game's strong suite.
It's more or less 1080P (900P for Xbox) quality wise. MSAA reconstruction basically means it uses the samples generated by MSAA to reconstruct the image. 2*MSAA means the game renders the opaque geometry edges at 2* the resolution and then downsamples it to minimise jaggies, since that's sort of how MSAA works (this is a slightly inaccurate description but I don't really have time to detail this right now). So at that resolution 2*MSAA brings the quality up to 1080P/900P if reconstructed.
You can check the quality of 1080P native without image reconstruction and by using 1080P with image reconstruction on PC and you'll see it's more or less indistinguishable.The only distinguishing feature is that the reconstructed image is slightly less temporally stable and causes minor artifacts when moving, but when used in tandem with the post process AA it makes it extremely stable...at the cost of image sharpness. Native 1080P with that post process AA is almost 1:1 similar to reconstructed 1080P with post process AA when compared side by side.
That is where the game gets its blurriness from...not the MSAA reconstruction.