There’s also a tool over on FMods for APIMs that got locked out due to having a VHTech cert installed when someone did a jailbreak of the APIM.
My take on seeing the 2016s showing up with extremely old builds that won’t update is that the certificate is now expired. A lot of the certificate tools before before Apple unilaterally decided to block certs over 13 months old would only allow a max code signing certificate life of 8 years.