if
If the BR is really saavy and decently quick, they will get themselves in a rundown deliberately, and make certain to extend it enough to score the run.
the BR in that case is simply trying to draw a throw.
if they are saavy, they are not running full speed, so they can reverse direction easily.
With all due respect, it doesn't matter. The slower the BR moves toward 2nd, the closer the defensive player let's her get to 2nd. A fielder running full speed straight at an oncoming runner will - short of making a mistake - always get to tag that runner before the runner can stop, change direction, and start back the other way. Always.