Thanks for the test, Christian. Thanks to your idea of using EmuTOS I could indeed verify that it works for me as well. But I wasn't wrong either; while HD Driver manual states:
With the "Devices and Partitions" dialog you can set which devices connected to which buses are searched for and managed by HDDRIVER it also states that
With “Auto Configuring“ HDDRUTIL tries to identify all connected devices automatically. I could swear that it used to work exactly as I had intended, i.e. that it would enable IDE 1.0 for me automatically.
Anyway, that's for an entry on Uwe's forum, nothing to do with Hatari, all good there.