Share buy backs raise the share price, but not market cap. so if you have 101 shares of Apple. And Apple buys 1 of those shares back from you, not much has changed as far as who has more value.
In reality, enormous swaths of shares are held by index tracking funds and everyday investors who don鈥檛 sell their shares into buybacks. In this case the market price based off supply/demand must rise in order to find someone who will let go of a share so Apple can buy it.
That is obviously not true and he's pointing out why - if the market isn't very liquid, in this case not a lot of sales, price can jump nonlinearly.
In theory if no one wants to sell shares of Apple during a buyback the share price will head towards infinity. There's always a price though that someone will let go of a share at.