Oh I figured out the reason is because the date is not associated with the record anymore. You can compare the page in the video to the record page and see the header is not on the record anymore (which is where the date comes from for the search, I guess). Someone else was talking about this on the form.
You are right about the reason why the record is not found that easy anymore: the date of the event has disappeared. I checked the current data record with the Groninger Archives (xml), and this lacks the event date. Which is indeed strange, as the FamilySearch tutorial video is "clear evidence" that the eventdata was present earlier :-) I'll reach out to the Groninger Archives to ask if they can look into the matter.