The Field Judge is the one who makes the call on the wide attempt, so he MUST have said something to the Back Judge. The BJ doesn't really look, and can't make that call.
I think this highlights the importance of backfield officials' communication.
In Canada, a wide field goal can be returned, and points are at risk (rouge), as well as other implications. The backfield officials should talk on who does what (if wide, the official on the other side bails for the goal line; if a blocked play or a fake, who covers what receivers, etc.)
And there should be chatter all the way through:
"snap ... ball is up... MINE .... WIDE ...<SIGNAL> , WIDE, WIDE ..."
"snap ... ball is up ... mine/yours .... " ("GOOD") - mutual signal
"snap ... ball is up ... YOURs ...." (react)
"snap ... GADGET ... GADGET"
"snap ... BLOCKED .... " at which point the officials move into other coverage.