Christians, Sikhs, Buddhists, Jains and "Others" - since my cultural background is a combination of some of those, I'm fairly confident that the author's perspective does not reflect my community, and likely some of the other minority communities, of which India has 7 million people.
I grew up in North India and I was taught to say thank you to friends and even to family members e.g., say thank you after being offered snacks (what would be called hors d'oeuvres in the west), offered a chapati or additional daal or sabji during meals, etc.
I did not say thank you to bus or cab drivers, but often did say thank you to shopkeepers.
Yes - just to clarify, my intent was to merely hypothesize at the idea that perhaps people ought to proceed with caution whenever some sort of behavior is categorized/stereotyped as "Indian", since in the case of India, even a minority is a very significant number of people.