General problem, as far as I can tell, is that if you're splitting a thick log you want as much of the length of the blade in as possible, so you might have to baton the handle rather than the blade. On a full tang, you're hitting the tang when you do this, but on a stick tang you're just hitting the handle which could cause it to split off entirely I would suspect, or bend the tang.
I don't think this should put you off stick tangs though - if you're going to be splitting logs that size, you should probably bring a hatchet or something larger like a Leuku anyway. If you do want one general purpose knife that covers all bases from whittling to splitting, you'd probably be best with a full tang. Otherwise, I'd say just a stick tang, a folder (or even just a small fixed blade) and a hatchet.
Peace