Different situation. MS has blocked off 3GB of RAM permanently that will only be used for OS partition functionality (I still haven't seen the words "3GB of RAM for the OS partition" come out of an actual MS employee's mouth tho, so unless there's a link somewhere that showed Marc Whitten or someone specifically say it, I believe it was just inferred from an interview with Whitten on Game Informer. If there's a link where MS actually announces the amount of RAM being used by the One's OS partition, I'd love to see that, because I don't think they have come out and said matter of fact that it is the case), so based on what we know, that 3GB will always be allocated for just that purpose.
The PS4 has 8GB of unified RAM that can ebb and flow between OS functionality and games, much like the 360 and PS3, so over time Sony can and is optimizing that RAM allocation for the OS, no doubt streamlining and shrinking it down like they did on the PS3 over time. I imagine they won't announce the amount of RAM allocated for the OS at this point because OS development will be something that's going up until the release of the PS4 and for the life of the console in general. Announcing RAM OS usage seems like a poor idea when even Sony likely doesn't have a number set in stone. It doesn't indicate that they are behind in development by any means, if the current console generation has taught us anything.