Edit: for instance, if Google has 200,000 employees and is granting an average of $50,000 stock per year, that is $10 billion. So id be okay with buybacks of that size.
The actual buybacks are much bigger if memory serves, so that seems like manipulation like you're saying
This is basically a net fiscal transfer from regular Americans to tech workers, since tech stocks are typically the default investment when retirement is more than a decade away, artificially raising the price of tech stocks.
Tech workers sell now while the price is artificially high and everyone else is left gambling later after all the tech workers have cashed out.