Why does big chip stack bb small chip stack more often than the other way around? It is very simple.
Because big chip stack tend to call more often with junk. pocket 10s all in short stack. big stack calls with 9 8s and has 20% odds.
you never see small stack calls this but you see plenty of big stack do it. And the results? every 100 hand callsed, you will see 20 hands of bb. It is simple as that.