I appreciate everyone's input. I'm always looking to improve my shooting abilities, my safety and my overall range conduct. If I had the frame of mind that "I'm always 100% right and the world is automatically 100% wrong" I wouldn't have even posed this question on THR, and I certainly wouldn't have bothered asking ahead of time to let me shoot the Ruger target pistol on the rifle range.
Just to clarify, the order for me to stop wasn't delivered over the range PA system, simply spoken by this person, faced completely away from me, while he was still seated.
Part of the problem is that the two fellows running the firing line are so grumpy and unapproachable. Usually the way to get people like that to treat you a bit better is to be proactive and say, "hey, I need something clarified" or "hey, I need a bit of a favor" - it reassures them that you are a rule-follower and recognize their dominion over the range.
I considered asking the fellow to clarify his remark, but I was offended by the way he didn't even bother to face me while saying it, in addition to not even being sure it was directed at me. It was NOT a PA-system call for everyone to cease firing.
Unfortunately, he was so standoffish that he made me feel like I was bothering him when I asked him to clarify some other detail from earlier in the visit, so that was my main reason for simply letting him come to me to repeat the "command."
When he did, I put the gun down, cleared it and cleaned up, without any further comment.