Coach fails to replace dq'ed player

[just another ref]

Tonight, boys varsity. Black number 50 commits his fifth personal foul. Partner reports the foul, then tells coach 50 has 5. Coach asks a question about the foul, partner gives a brief answer. Coach nods. Everybody seems satisfied. But coach just keeps standing there. 50 keeps standing there on the court. Partner says 20 seconds. 5 seconds....horn 15 more seconds...horn Partner call a T on the coach for failing to replace his player. BUT, 22 black was standing at the X waiting to check in before the foul was ever committed, and continued to stand there until after the T call. Partner apparently wanted the coach to specify that 22 was to replace his fouled out player. I said as far as I knew, the coach had a sub standing on the X, so no further action or comment was necessary.
Right?