Arizona/Stanford game last night.

Anyone watch the game see the play in I think the bottom of the 4th. Stanford had runners on 1st and 2nd and I think there was 0 outs. Ground ball hit to F3 batter-runner instead of running into tag stops then takes 2 small steps backward and is then tagged out. Batter is out and runners that advanced to 2nd and 3rd returned to original bases.

Is this an NCAA rule or is it an ASA rule? I had never heard of this before.