You need to see with Dave on Kodi forums why the option is missing in the GUI.
That settings is supposed to be there and returned to Yatse. Not much I can do about Kodi GUI side 
I think I found the setting for advancedsettings here not long ago and introduced it into my file:
https://kodi.wiki/view/Advancedsettings.xml#musiclibrary
It says there that the setting is available since Kodi 18. Is it possible the GUI setting is only available with Kodi 19?
Nevertheless, I readded it to the file. Kodi shows the proper sorting, but Yatse still does not.
And I am so sure that this worked until recently…
I use Kodi 18 to reproduce with your DB the setting is present in Kodi 18.
Yatse can’t ask advanced settings but can check Kodi GUI settings.
Remove from the AS.xml restart Kodi the GUI settings will maybe be present in that case.
I think there’s a thread about those in Kodi forums and in all cases Dave there can help with the missing GUI setting he added everything related to it.
Now you pointed me to the right spot: removed it from AS.xml → setting shows up in the GUI again. Synced Yatse → result as expected!
Thank you! So this was another self-made problem. I think I stumbled upon the Kodi wiki page a couple of weeks ago, and without thinking much about it I introduced the setting to AS.xml unnecessarily - and with that broke Yatse myself.
Thank you for your support. It is not easy to see through all the dependencies.
I completely forget there was an AS settings and that this would break the GUI 
Joys of Kodi (And some nice decision about preventing access to AS from remotes by a now gone very nice Kodi Team member ;))
Both indeed hard to understand…