Rumor? I think it's just an attempt at simplification of a complicated issue.
You can read for yourself Microsoft's Technical Fellow Mark Russinovich's explanation at
http://blogs.technet.com/markrussino...1/3092070.aspx
32-bit Client Effective Memory Limits -
While 4GB is the licensed limit for 32-bit client SKUs, the effective limit is actually lower and dependent on the system's chipset and connected devices. The reason is...<snip>The result is that, if you have a system with 3GB or more of memory and you are running a 32-bit Windows client, you may not be getting the benefit of all of the RAM.