I dont think this is a mistake, the text is very explicit and there is no posible error in it (the text is in portuguese or brazilian, im spanish and understand it perfectly)
Also, i dont believe people that says "PS3 cant do cross-game chat because there is no enought RAM"
Who are they to decide where are the restrictions and limits ?... are they software engineers that worked for sony ?... they designed ps3 hardware or software ?... are they blind and dont want to understand that you can have more ram by disabling other process ?
So in the end... is a problem of the ram available, but there are other ways to free ram, like reducing the load of other process, improving or removing them (XMB in-game is the bigger resource devourer, and is not efficient)
So simply by disabling XMB in-game you can free ram.... note that there is a flag inside .SFO to disable "XMB in-game".... and another flag to disable "chat"... these flags are very conveniently placed there, and can be "reused"
My bet is "cross-game chat" in PS3 is more than possible... i also think they have it working internally lot of time ago (this is the reason why this flags are there)
Note that sony bigger competitor (XBOX360) does cross-game chat... so is (or has been) something prioritary for sony to implement in PS3, you can bet for sure sony was working in it lot of time ago