Update iPad 5th gen from 15.7.1 to 15.7.4

For future debugging I want to keep one of our iPads 5th Gen (MP2F2FD/A) at a 15.7.x version, it currently has 15.7.1 installed. With Apple Configurator 2 or via Finder there is only the "Newest" (right now: 16.4) option available. I tried to upgrade via our MDM to 15.7.4 but it's management history doesn't show any "Schedule OS Update" command as pending or finished. The overview here: https://en.wikipedia.org/wiki/IPadOS_version_history shows an 15.7.4 version, but https://ipsw.me/iPad6,11 doesn't show this version and shows the latest 15.7.x version as unsigned. So it seems that there is no signed version of 15.7.4. Why is there no version 15.7.4 available for this iPad?