Restirct user access to SPO Root SiteCollection

Hi everyone,

In a tenant, the SharePoint Online root site collection was deliberately locked down to a very small audience.

We are currently seeing some issues that could be related to this. While investigating, I noticed that some Microsoft documentation seems to imply that the root site collection plays a special role and should be accessible for the users, for example:

• https://learn.microsoft.com/en-us/sharepoint/modern-root-site
• https://learn.microsoft.com/en-us/troubleshoot/sharepoint/sites/url-that-resides-under-root-site-collection-is-broken

However, I couldn’t find any explicit or official recommendation stating whether restricting access to the root site collection is supported or discouraged.

So my question is:
Is it a best practice or implicit requirement that the root site collection remains broadly accessible for M365 / SharePoint Online to work reliably?

Thanks!