Not true, of course, for the Good ones. As an example Superior Drummer 3 gives the choice of either programming manually left/right hits, or adopting the 'Alternate Hits' function, which, as its name implies, triggers samples alternately (useful for double bass drum 'blast beats', for instance...). With normal 'round robin' sample triggering and 'humanised' velocity levels, it would be difficult to tell whether it's a machine or just a very good drummer, most of the time, without a specific 'right/left' precision, but it's there if you want/need it. Other drum software have similar functionality (BFD, Slate and others still...).
When practising drum rudiments, using 'mama-papa' strokes and/or paradiddles, one of the aims is to have an even 'hand', so as to not hear a difference between the two hands. It's not the easiest of exercises, and is often neglected, but in theory at least, one would not hear any 'right/left' from a Good Drummer, so it's a bit of a moot point as to whether software should offer it or not. Listen to Buddy Rich, Joe Morello, Terry Bozio or Dave Weckl (other brilliant drummers exist...) and I defy you to tell which hand/foot they're playing any particular stroke with.
Just sayin', hope this helps.