Scott Roberts posted the following two posts over on WSUS Product Team Blog and seeing that you might have wondered about those, here they are:
Intelligent Message Filter for Exchange Server 2003: Release cycle begins on the 17th of this month
Intelligent Message Filter for Exchange Server 2003: Supersedence release model
That might explain recent changes that you have seen with IMF updates!
Updated Jul 01, 2019
Version 2.0
