A criminal will be a criminal.
Better be safe than sorry. Just be cautious and aware of your surroundings. I like the idea of using the phone instead.
I have heard of the chopping arm tactic before from my Hong Kong friends in the 90s....apparently it was an era of rampant triad activities. That's what I heard.
While I doubt the Indian chap is going to chop off your arm, but do be careful of hynopsis and illussions. I have heard stories of con artist who are able to hynoptise their victims.
Was in Bangkok last year, window shopping at the high-end watch boutiques of Paragon and similarly had an Indian guy walk up to me suddenly and telling me I have good face feature and very lucky with many blessings, etc, etc. I just walked away.