How does it differ from the CACHE command or what's turned on with SetPatch and the CPU command?
I suppose these are options for within the "virtual" system that WHDLoad starts, and not the "host" system.
Btw - you know that with WHDLoad you can boot into OS3.1 or OS3.1.3 from OS3.9, with a defined directory as boot disk for the "instance", run programs in there, and at any time press the defined exit key to shut down the virtual OS3.1 or 1.3 "instance" and be back in OS3.9? Very convenient for running programs that somehow struggle with OS3.9, or as a test environment for your own hackish asm code
http://www.whdload.de/apps/alla.html