I wouldn't generalize to like, the entire nations of India and Tibet, but it's an _extremely_ common phenomenon even in the US, even today. Just look at how many spurious quotes are ascribed to "great thinkers" (abe lincoln, gandhi, albert einstein). It happens even with relatively contemporary figures when we have voluminous historical evidence available to disprove it -- imagine how often it happened before the internet and printing press. I have this pet theory that the origin of the https://en.wikipedia.org/wiki/Q_source was just someone trying to write down all the stuff that anybody anywhere said that Jesus said in one place, so that people would stop making up shit.

Buddhists still do it (called "terma"), but I don't think it's necessary to call your secular philosophy works Buddhism anymore.

And of course people in the US often make things up and call it ancient Asian wisdom too, but usually aphorisms rather than whole books.

Not in present day. Our values are 180 degrees from this, it is better to claim novelty.

Rather the question today is OMG why do we care about 1000 years ago, we are more advanced!1111, whatever problem ancient people had, we have solved.

Which is equally silly