Hey @Kwoodhouse, sorry for the confusion. The fix does rely on your host reporting system uptime as defined in the Host Resources MIB (specifically, hrSystemUptime at .1.3.6.1.2.1.25.1.1.0).
If that doesn't OID doesn't return anything, we fall back to using snmpEngineTime. This isn't necessarily the uptime of the system, but rather the uptime of the snmp agent, and it will reset with the agent even if the system does not reboot. The fix was never ported to the module that retrieves Engine Uptime, but it should be easy enough to do. I've put a fix in with the ME team to get this done.
I did go ahead and update the alert message in the meantime. Thanks for bringing this to our attention!