This situation looks like Google allowed Spotify to add their own payment system with some terms. The obvious one is that they need to keep Google's payment system alongside their own. A less obvious (but IMO likely) requirement may be that Spotify cannot offer a much lower price through their billing system to incentivize users to switch (100% assumption here).
From the outside, this looks like a pro-consumer move: consumers get more choices (even if the prices are the same). But the reality is (probably; I'm just assuming here) that Google still has the power to shove their billing system down developers' throats, since there aren't yet any laws or rulings to prevent it.
So even though the writing in this press release makes it seem like a pro-consumer move, I hope it doesn't take any momentum away from all of the antitrust lawsuits. Google's (and Apple's) monopolies need to end. In an ideal world, Spotify would add Google billing (and others) as options to attract more customers, not because Google is forcing them to.