It wasn't really a rumor. It was pretty much true that the system had 4GB of RAM. So yes, I think Microsoft felt they were comfortable where they were. Plus it's always easier to reduce the reserved resources than it is to ask for more. In fact it's near impossible to ask for more. 3GB is obscene for what they're doing I think so I can almost guarantee you that will go down in a short period of time.
Again, you're missing the big picture. It's not about what Sony said first. It's about how Sony's schedule of revealing information of the PS4 played out and how Sony is taking advantage of the current situation. They planned to show games first and services at a later point in time. They now get to take advantage of the fact that they showed games first, still say services are coming, but play off of Microsoft's screw up. I'm not saying Sony is changing focus. I'm saying Sony is taking advantage of a situation that plays favor to them. That's not to downplay all the great things Sony is doing to work with developers. Heck I know for a fact that they are based on first hand knowledge. That doesn't make this any less of a good PR opportunity for Sony though.
Honestly, I'm definitely not an Xbox fan. Heck, I'd recommend people getting a PS4 over an Xbox One. I just think some people are putting emphasis on the wrong things.