By definition, BS is defined as the optimal play to make with knowledge only of your first two cards and the dealer's upcard. It makes the assumption that those three cards have been removed from the pack (as opposed to a "thought experiment," where you would think of those three cards but keep them in the full pack).
So, the count after those three cards are removed will not always be exactly zero. In the case of 16 v. T, where you need a TC of at least 0 to stand, BS is to hit, because there is no way you can have 16 vs. T where the RC -- and hence the TC -- won't be negative. For Hi-Lo, the RC will always be -1, and the TC will be -1/x, where x is the number of decks you're playing against.
Clear?
Don