From what I am reading the “tamper protection” feature was actually launched last December (for business customers) and is now being rolled out to Windows 10 computer user’s at home that are running Windows 10 v1903.
At the time of this posting, I checked my Windows Defender software on my PC and have not seen anything thus far to indicate “tamper protection” has rolled out to my PC.
Tamper Protection, as the name suggests, protects certain security features from tampering. One of the barriers that Tamper Protection puts in place around security features blocks manipulations of setting changes that are made outside of the official Settings application. Attackers may attempt to disable real-time protections or certain security features and Tamper Protection was designed to prevent these changes from being made successfully. — Source: gHacks