System files are owned by TrustedInstaller . You cannot modify or replace them until you take ownership.
It is often used by small businesses or home labs to avoid the licensing costs associated with official Microsoft RDS deployments. How to Apply the Patch on Windows Server 2012 R2 universal termsrv.dll patch windows server 2012 r2
The patch bypasses this fallback by altering the comparison instruction. System files are owned by TrustedInstaller