In the Play Store, find the Drive app, select "About this app", scroll down to "App permissions", and tap "See more". It does not have the "manage external storage" permission listed, which is the one Nextcloud says they need.
Right but it doesn't do the same thing Nextcloud does. If it did do you think Google would say to the drive team "sorry you can't do that"? Of course not. They'd invent a new permission or just whitelist Google apps (they've done it before).
It's a lie in plain sight, because for most Google apps, including this one, a lot of background processing is not done by the app itself but by the Google play services app that is all powerful.