[mbyron]

Originally Posted by just another ref

But if the thrower stands in the spot a couple of seconds, then enters, how does this gain an advantage?

Answered in the OP:

Originally Posted by rfp

Inbounder B1 passes into the corner and then remains out of bounds for approximately 3 full seconds, in what appears to be part of their inbounds play strategy, so the defense loses attention on her. After 3 seconds she comes inbounds at the box, receives a pass and puts up a lay-up for the go-ahead score.