I think the idea is any s3 compatible api endpoint can be used. The code also clearly supports both backblaze, and more importantly, local blob storage
Buyback programs are at the then-current publicly traded rates. They aren't generally at some magical premium, or else the whole trading price of the stock would go up even more.
Most people selling their shares in a company do not know who is on the buying side, and that is generally the case here. This goes for retail and institutional investors. And the buy-back programs are done slowly to avoid slippage, which can make it even harder to track down in the moment.
Someone who wanted to sell was selling anyway. They don't profit any more than their gains (or losses) already covered. The people who get "value" are the ones who did NOT sell their shares, and their "value" is only realized down the road when they do eventually sell.
A stock buy-back increases the stock's value through scarcity. It does not actually "return cash" in any immediate sense. Any value increase is completely on paper. The holder of the stock is still taxed when they sell their shares.
This is the same concept as you owning a home and someone builds a nicer home next to you. Your home value just went up. But you don't have a cent of that money until you sell your home, and then you are taxed on the gains (unless you roll it into another home, but that's a separate discussion).
The Chicxulub crater off the top of the Yucatan peninsula is attributed for that particular event. It wasn't really known until the early/mid 90s I don't think.