We used tandem UR, ball activation on top and flow activation below (rat hole elimination system) for the same reason you mentioned: to have the LWD tools below the UR in small hole section while drilling.
We dropped the ball after drilling out the shoetrack, LOT and when the UR was in OH.
One of the reason as you wrote is not to damage the casing... and also the UR cutters even before starting to open the hole.
In the case you mentioned, they maybe installed the ball before RIH on a subsequent BHA after the shoetrack was already drilled out... or drilled out the shoetrack with reduced flow rate to have an insufficient pressure differential at the UR... But I do not think the time saved by installing the ball before RIH is worth the risk.