I guess I could be wrong, but I thought that was only for DOSSHELL itself, not for the tasks you were launching. Perhaps it would work but only if the other tasks supported it?
My quick test of running multiple command prompts and running free showed that each one had a full set of memory. It's not multitasking, and I believe it assumes that the tasks are well behaved (not modifying DOS internals), so tasks don't really need to do anything special if they are well behaved.