Agreed. There is no conflict between the BOL references. One states the maximum memory requirement for installing (and running) SQL Server Workgroup Edition, and the other statest the maximum memory SQL Server Workgroup Edition is actually capable of putting to good use once it's been installed and is up and running.
Yes, it's a subtle difference, but a perfectly reasonable one. Just look at the converse - if you installed SQL Server Workgroup Edition on a box with 512Mb RAM, then removed 256Mb and upped the page file by 256Mb, SS2k5 won't fail to run; it'll just run like a dog. Running requirements and installation requirements are two separate things.
Semper in excretia, sumus solum profundum variat