Spot prime indoors with shellac-base primer?
I've used BIN primer with great success in the past.  The reason the can says to use under a high-hiding paint or to prime the whole surface is so the primer doesn't show through.

Say you have some unpainted, knotty wood and you spot prime the knots.  When the whole board is painted, the spots where the primer is will be very obvious since they are bright white and absorb the paint differently.

I've used BIN to prime an entire wall of knotty pine, smoke stained paneling and then painted.  It worked well since the whole surface was evenly primed before I used the paint.

For what it's worth, you wouldn't want to spot-prime over normal stains on an old with a water-based primer before painting either.  You'd prime the whole wall or you would have an inconsistent sheen at least, and visibly lighter spots in many cases.

Looking back at your question, since you are going to be spot-priming a previously white-painted surface and you're going back over it with the same, white paint, I think spot priming with BIN should be OK.  Just be generous with the spots so the stain doesn't travel under and around the BIN spots.