The issue: in earlier production releases igdlh64.inf contained the SUBSYS numbers (subsystem vendor IDs).
After those earlier version are installed, your later production releases without the SUBSYS information are deemed to be compatible but not updated versions of the driver. You'd have to force install, instead of the usual route.
After further investigation, I found out that this is expected behavior with the Intel generic drivers. You can find the SUBSYS numbers in the OEM (Original Equipment Manufacturers) drivers but not with the Intel generic ones.
The OEMs can customize the equipment so that only drivers with their SubSys information can be installed (i.e. 4id).
In contrast, all generic drivers available in DownloadCenter will be only 2id, meaning that there won’t be any OEM information in place.