Yeah that seems to be the case, unfortunately.
But, after quite a while of experimenting, I found out it still works with a virtual lock - literally ‘lock’. There’s no ‘unlock’ available for Ggl routines as far as I could find.
EDIT: setting device class to “Kettle” works great.
With the avd settings, I use the shower light (“Spiegel lamp Badkamer”) to control the lock, without any flows:
Google Home:
The lock triggers the routine which starts a Spotify playlist on a Ggl mini speaker: