It does something. If you have the text console open (use /console 1 first), it causes the following text to be printed on it:
"Not using private parser heaps."
The command description from cmds* seems to indicate it has something to do with memory allocation, but the actual code path in the exe just prints that message. It's probably something that was #ifdef'd to only work in debug builds or something along those lines.
* Not that the command descriptions are very accurate, especially for developer (accesslevel 1-9) client commands... Many of them depend on server-side support, do nothing, or do something wildly different than what the name or description would suggest.