I have not run across that limitation before. Could you perhaps let us know where you found it so i/we can get some more information?
The item in question is a Seagate Free Agent GoFlex Desk External Drive, 2TB; for Mac OS X 10.4.11 to 10.6.2, 32-bit kernel only; UPC 63649 02341.
Moreover, no external drive which I have seen so far has indicated a compatibility with OS X Lion; the latest version of OS X applicable has been 10.6.x.
