It is only negative interest if the stock goes up. It is positive interest if the stock goes down. So you could call it a variable rate loan to invest in the company's stock. I would not choose to take out such a loan against the growth rate of the company I also rely on to pay my salary.

I would actually like RSUs more if they granted me shares in a basket of stocks of competitor companies. At least then it would hedge my already high exposure to the fortunes of the company I work for.

If the stock goes down, you can walk away from the arrangement without being on the hook for anything. If it goes up, you collect a salary while having exposure to the company stock without having to put up any of your own capital.

I am not seeing where the positive interest is here.

Relative to just being given the cash instead of the equity.