The deferens is that the BILL-1 is gong 80cm above the "sight line" and have attack system which is directed 45' down. BILL-2 is flying 2m above the "sight line" and has got a multiple charge. The charges are directed ~90'.
More about the BILL-1 is that Bofors has shooting through 1m steel.
When I was at Kråksskjutfält we did shooting through a Strv-74. The hit was on the back of the tank, going through the engine and out on the bottom.
IIRC, in the game Top attack ATGMs,class 20, are assumed to be multicharge weapons as well,which makes sense to me.
At any rate those TOW-2Bs go throught the top ERA of my fictional MBTs as if it was not even there...