What causes a flag to expire?
They expire after 3 or 10 years after the incident (based on the type of the flag).
[...] A new scammer flag should be created for each separate alleged incident. In the spirit of forgiveness/redemption, scammer flags expire 3 years after the incident if the contract was casual/implied, and 10 years after the incident if the contract was written. These expiration times might be administratively changed in specific cases. [...]
This specific test flag's "incident date" is May 2016.
[...] It is not grossly inaccurate to say that the act occurred around May 2016 [...]
So, 3 years after the incident (May 2019 in this case) the flag would have expired.