Poaching my signal?

[Amesman]

Worked with probably my favorite partner this weekend -- knowledgeable, sharp, in it for the kids. Just a good guy who should be getting more top games, in my opinion. Probably no coincidence assignors pair him with me so they have their behinds covered with at least half a crew that knows which end is up.

Anyway ... just wanted to see what the board thought of a minor sequence we had in a free-throw scenario. I'm L and bounce the ball to the FT shooter. After he has the ball and as I'm backing out of the lane, one of his opponents above the top of the key decides to occupy the top lane spot opposite me -- in what will be/is my coverage area (basically right in front of my partner).

Partner is all over it and gets the arm bar out while I'm still backing off the court. The FT shooter converted so there was nothing to enforce. But my question is: Was he appropriate in taking that call? I saw it and would have signaled once I was behind the endline. And should I have mimicked his arm bar once I was in position anyway?

Don't know if it's really worth a hill of beans since he had the situation covered. But don't know if it might ever come up again -- with a partner at T who would purposely NOT signal in this situation on the basis that it's my call to make.