BR collides with F3 after catch

[youngump]

Originally Posted by IRISHMAFIA

My issue with the play and applicable rules is that there was no interference. As noted, the runner did not break for home until F3 was knocked to the ground, so at the time of the collision, there was no play with which to interfere.

(Bold mine) Why does the bolded part have to be true? It seems to me the most minimal stretch is to treat this the same way we treat obstruction. It's actively happening until the runner recovers. Thus a runner tripped going around second just before getting to the base who falls between 2nd and 3rd was obstructed in between both 1st and 2nd and 2nd and 3rd. A fielder knocked down is actively interfered with until she recovers (but it wouldn't be a play if there was nothing to do in that time period). Usually that doesn't matter because the interference kills the ball. Here it would matter.
I'm not necessarily arguing for this (though it makes the most sense to me) just asking why that isn't the best reading of the hole in the rules.