The first reference indicates the SObjects where an APEX class can not perform DML statements like insert, update, delete, upsert or the equivalent
Database.insert(..), etc method calls.
UserTerritory are excluded from APex DML.
The second reference is a list of all SObjects available for manipulation by the SFDC SOAP or REST API
However, an APEX class can use the SOAP or REST API via Apex HTTP callouts upon the same org and do the DML operations permitted in the second reference. In your example, for SObject
create(), delete(), describeLayout(), describeSObjects(), query(),
retrieve(), update(), upsert()
That said, you won't be able to mock any testdata for these SObjects in a testclass; instead, you'll have to mock SObjects in memory.