Microsoft Bookings - Email reminders not sending

Question

I have a Microsoft Bookings calendar for my business to manage the various appointment types that are on offer to our clients. Some are linked to a Teams meeting, and some are not (face-to-face), some use physical resources (such as a therapy room) whereas some take place in clients' homes or similar.

For operational reasons, some of these appointment types are shown on the organisation's booking page whereas some are not published; this is so that the business can control what resources are being used and for whom.

What I have noticed is that the reminders that I have set up in the "Reminders and notifications" section of the "Edit service" page do not get sent if I arrange the appointment myself, booking either on the Settings>Services>Book Appointment page or the Calendar>New booking page. I have experimented with all of the options I can find, including the 'Let customers manage their appointment when it was booked by you or your staff on their behalf', but nothing there seems to enable the reminders to be sent out.

If I go to a (published) Service booking page and fill in all of the details on this, then the reminders come out as expected, but as I don't have all of my services published, I'd need to leave them published all of the time and this poses too much risk that clients will make inappropriate bookings.

Why aren't the reminders being sent when the appointment is booked on behalf of the client?