Why don't I know?

referee99

Ball is loose on the floor.
Players A1 and B1 simultaneously grab the ball, B1 stays put, but A1 starts moving feet, anticipating that he will start a dribble.
B1 never lets go, no held ball is called, as its not warranted. (just simult. holding, no rough play imminent.
Can A1 be called for traveling?

4.44.2sitB addresses 'joint control' by teammates. Do B1 and A1 have joint control here?

GoodwillRef

Call a jumpball and move on.

OHBBREF

referee99 wrote
Players A1 and B1 simultaneously grab the ball, B1 stays put, but A1 starts moving feet, anticipating that he will start a dribble.
B1 never lets go, no held ball is called, as its not warranted. (just simult. holding, no rough play imminent.

So what your saying is that you are not calling a held ball because they are standing there and not struggling for it. So by that logic if A1 moves her feet she has traveled and you give the ball to team B.

I think you are concentrating too much on the "control cannot be obtained without undue roughness." part of the definition.
IMHO If two girls are simultainiously holding the ball - call the held ball and go to the AP before it results in undue roughness!

SAK

If two players from opposite teams both have their hands on the ball a walk cannot be called. Neither team has possession, by definition you cannot have a walk without having possession of the ball.

Rich

SAK wrote
If two players from opposite teams both have their hands on the ball a walk cannot be called. Neither team has possession, by definition you cannot have a walk without having possession of the ball.

What's a walk?

OHBBREF

SAK wrote
If two players from opposite teams both have their hands on the ball a walk cannot be called. Neither team has possession, by definition you cannot have a walk without having possession of the ball.

not true, Team A has the ball in the front court, A1 passed the ball and it deflects off A3 and grasped by A3 and B3 simultaniously unntil you call a held ball Team A has not lost possession, the shot clock would continue to run and would not reset if A3 pulls the ball away from B3. So there is not a loss of team control until the official determines there is a held ball.
Also if I have two players holding the ball and one is dancing all over the place I am going to have to either call the Travel or the held ball.
So going back to the OP where using the control can not be obtained by roughness etc. is not going to call the held ball you have to call the travel because themoving player could gain an advantage.
that is my point.