From the above blog entry:
To our knowledge, iMazing is the only non-Apple software to enable users to download their purchases from the iOS App Store. We strongly hope that Apple won't block iMazing's app download capabilities: we've done our best to provide tools which many iOS users truly need.
I haven't tried this fantastic idea of iMazing's yet, but frankly I suspect the functionality won't work for long. I expect Apple will indeed block this capability, because Apple doesn't want general users to have an easy way to run older apps, which could be a security risk (iTunes 12.7 removes ability to save .ipa files to PC).
But kudos to iMazing!