R3 tag, 2 man crew

[orioles35]

R3, less than two outs. I'm PU, BU is behind the mound.
B1 hits a pop-up to the edge of the grass to the left of F4, R3 gambles, tags and scores. Appeal to 3B following the play, I point to BU who was watching the catch. Coach gives me an earful, saying "that's your call".

Since there was a R3, isn't that the BU call? I have to stay at home in case of the play at the plate and besides, no matter how much I move down the line to see if R3 leaves early, I'm never going to see separation between R3 and the bag, certainly if I'm going to be making a call at home.

This wasn't a play where the ball went high enough that the BU could position himself where he could see the catch and the runner. Is this simply a limitation of a 2-man crew?