From the article:

But Epic v. Google turned out to be a very different case. It hinged on secret revenue sharing deals between Google, smartphone makers, and big game developers, ones that Google execs internally believed were designed to keep rival app stores down. It showed that Google was running scared of Epic specifically. And it was all decided by a jury, unlike the Apple ruling.

It’s not that it wasn’t technically possible, Google just made moves to discourage other stores directly with phone manufacturers and developers.