You can sideload apps, whether they are on the blocklist or not. That’s what the sentence* you quoted says. Well, that’s what I interpret anyways. Maybe I’m wrong.

You misunderstand, the list of apps they block are “inside” the said list, while sideloading apps “outside” of the said list is possible. So you can only find and install whatever apps they’ve approved within whatever app store they use to serve apps to their customers, but you can install any apk on the phone by sideloading it, given the app supports the phones CPU architecture of course.