They could just pay dividends, but then some argue those would be taxed at time where as buybacks are only if sold later at profit.
They're taking actions that raise the stock price. That hardly counts as manipulation. (It would count as manipulation if the buyback were conveniently timed to coincide with share-price incentives.)
Assets decrease. But so does the share count. This tends to raise earnings per share while decreasing assets per share [1]. (Liquid assets, particularly [2].) Meanwhile, there are signaling and liquidity factors which raise the theoretical value of the company.
In summary, there is no rule that says a buyback should be share-price neutral. (The same for special dividends.)
[1] https://www.nasdaq.com/articles/does-stock-buyback-affect-pr...
[2] https://business.inquirer.net/238377/share-buybacks-affect-s...
A buy back is only taxed as personal income when granted to the employee.
I'd be curious to see a study supporting this claim.
This is how it works. It's why companies report an earnings per share on a fully-diluted basis.