The terp was saving time. Other terps do it, too. Anytime I see a name beginning with "R" I watch for a "B" (Robin, sister) or a "D" (Richard, best friend). When the terp fingerspells the first word and it contains a "V," I know that the caller just said, "Hi, Melvin!"
Also, I had a lengthy conversation in which "Barbara" came up several times. Her name was fingerspelled the first time. On subsequent mentions of her name the terp just shook a "B." She was the only "B" name in the conversation. I followed suit during the next call I made. I signed "dry cleaner" upon the first mention of them. After that, I mentioned them again by spelling "D-C." I probably should have shaken the "C" to kind of clue the terp in that I was using an abbreviation, but she got it anyway.
Now, it's just interesting to see what shortcuts the terp will take to keep the call going at a smooth pace. Only, I wish some of these websites that teach fingerspelling would mention this phenomenon so we would not be surprised and bewildered by it.