Is it at all relevant, whether the initiator is or is not the organizer?

I think it's not relevant. The modified code before the change was setting _notify flag when edited/new event has any attendees, no matter the user is organizer or the attendee. In comparison with the php code which calls notify_attendees() when _notify flag is set, it does not make sense. So, I modified the code to not set the _notify flag if the originator is an attendee.

However, when I'm looking at this closer I see that still might not resolve the issue fully. The issue talks about a case when there's organizer and one attendee, what if there's more attendees? has_attendees() will return true and notification to the organizer still will not be send. More work on this needed.