I'm hesitant to test this feature and wanted to ask if you could clarify something.
The default text in the still empty textarea says at the end: "Please double check your current IP address before saving to ensure you are not locked out."
I'm not 100% sure what area I would be locked out of. My interpretation and worst case guess is that "locked out" is implying a non-reversible setting by also applying the access control to the Admin Center - otherwise there would be no "locked out" situation.
I see three indicators that the Admin Center is not affected by this setting.
1) Text in the subheader of the configuration page: "These settings apply to content in SharePoint, OneDrive and Office 365 gorups."
2) Text in your post above: "These policies ensure content can only be access when someone is connected to the defined network" - assuming by "content" you are referring to the same content referred to in the subheader of the configuration page.
3) 1st FAQ in your post above: "Location-based policy, as configured through the SharePoint Admin Center are limited to SharePoint Online, OneDrive for Business, and Groups."
Those three indicators lead me to believe that the Admin Center is not affected by this.
Then again: If this is the case then there it is impossible to lock myself out of anything.
I would appreciate if you could clarify this little detail before I'll go ahead and test this ;)
Thanks & Cheers