I understand what you're saying; I wonder if we're envisioning two different plays. I consider tripping an "active" act, where an arm or leg is put in the path of a moving player. Perhaps the play you are picturing is where A1 receives the ball, then B1 goes down as A1 starts their move. B1 would still be moving, or had just gotten to their knees at the time of contact. I would agree this could fall under tripping and/or rough play. The play I was picturing was B1 going to their knees as the pass is coming coming to A1, and there is a pause before A1 starts their move back. Iow, two separate acts; A1 would have easily avoided contact if they had looked back. That's where I can't see penalizing B1 if they have their spot on the floor that was obtained without contact.

Let me throw another (admiitedly third-world) twist in this: you have already called B1 for a block/trip on this play earlier in the game. The coach, being a persistent a$$, tells B1 to try it again. A1, knowing what happened before, this time turns around sees B1 go down, and purposely runs over B1 to get the call again. B1 is again motionless on their knees, but this time A1 sees them. Do you make the same block call again? How does intent change the call? What rule do you point to that shows how intent changes the call?

And, yes, that coach wouldn't have been as persistent had the team-control foul been called earlier.

1st time, I call the pf and warn the coach. 2nd time, I call the T on B1.

I realize I'm a bit late in the game posting on this, but to me, this is at LEAST an intentional personal foul and very possibly a flagrant personal.