But I don't believe in it. If I were the scammer, I would have maybe 2 or 3 of these lengthy talks with "her", but afterwards I would recognize her and of course avoid her anytime.
That "fleet" would need many significant differences, like when you recognize different people, then many features are different. If your grandma talks to you with a different tone, you would still recognize your grandma easily.
Depends on how much effort the average scammer puts into remembering the prospective victims that don't bite. My guess is that they don't waste too many brain cells on that.