Because the rules (or a case play) specifically allow it.

Why is this question false?

The implication is that he actually pushes A1 with both hands so it should be either an intentional foul or a flagrant foul. I probably should word this differently to give that impression. I can see that it could be taken as just a common foul the way it stands. Thanks.

4.44.5 SITUATION B: A1 dives for a loose ball and slides after gaining control. A1 is in a position either on his/her back or stomach. What can A1 do without violating? RULING: A1 may pass, shoot, start a dribble or call a time-out. Once A1 has the ball and is no longer sliding, he/she may not roll over. If flat on his/her back, A1 may sit up without violating. Any attempt to get to the feet is traveling unless A1 is dribbling. It is also traveling if A1 puts the ball on the floor, then rises and is first to touch the ball. (4-44-5b)

It's also a violation if A1 moves his/her pivot cheek.

I had a V official, who was working the table at an AAU tourney, tell the opposing coach and then myself that I should have been calling 3 seconds on his player. He argued that when the player shot the 3 second count "freezes" and when he gets the ball it picks up where it left off, and then said to me "You should check that out, brother". I was shocked and didn't respond well. I laughed at him and told him I didn't need to check it out and maybe he should check out the 3 second rule, and then remember there is no team control during a shot. I can't believe he made it to Varsity with such a distorted view of a basic rule.