3 man rotation question

[CecilOne]

Originally Posted by IRISHMAFIA

The highlighted line is a little confusing.

PU needs to take this runner home. Since there was no play at 3B s/he should not have needed to commit to 3B. The only negative is that the PU must be aware s/he cannot move into a position between R3 and the plate

Now I'm confused.
My understanding, based on someone being ahead of the lead runner, is the PU covering 3rd, regardless of where the fielders are
and the U1 rotating home when the PU does that, even if late.
Then, the PU can judge where the play is going; possibly call off the U1 if the U1 is too late.

Additionally, this shows the value of BOTH pre-game and pre-pitch.