Question

I know that sys schema has execute access on all extended stored procedures.
If my sys admin logins are having schema – dbo, what is “sys” schema used for?

Or can I deduce that sys admins have execute permissions on all extended stored procedures?
How can I prove it with tsql?

Answer 1

sys‘ is magic. Is recognized in code as special and it looks up its contained objects in the special resource database:

SQL Server system objects, such as
sys.objects, are physically persisted
in the Resource database, but they
logically appear in the sys schema of
every database.

The ordinary ownership and permission rules don’t apply to sys.

Sysadmins don’t need any permission, they have all privileges and cannot be denied nor revoked anything.