Corporations doing stock buybacks are the exact opposite of hoarding cash.

They have excess cash that they do not believe they can effectively use to expand the business or go into new ventures. So they send the cash back to the investors, either by direct dividends, or by doing a stock buyback which increases the value of the remaining shares (equity per share) by the same amount(modulo any tax consequence difference between long term capital gains/dividend treatment.)

A corporation hoarding cash would look more like keeping billions of dollars sitting in banks accounts above-and-beyond what is needed for working capital and expansion needs, while refusing to pay out that money in dividends or by buying back shares.