I don't get what part of that your think enables them to deny access to third parties distributing their apps on alternate stores. If you're referring to the last paragraph, that very explicitly says that any such security must be an optional setting that is not default. So unless users opt into verified only apps, Google can't force that, according to the DMA.
Maybe not, but reading their blog posts about ADV next to the DMA text, that's certainly the angle they are trying. And it will be years if it ever comes to a court hearing.
And the setting is "optional", just do the 24h-waiting song and dance to change it, or use ADB. /s
