You are correct, you should be able to share info and support others…. BUT only where the forum members have the knowledge to share with others.
In general, members on this forum are very knowledgable and very willing to share the knowledge they have, but there are times when they are stuck. So many technicalities with modern day cars such that trying to keep up with things can be very difficult, sometimes impossible.
The hourly rate at a main dealer, no matter what manufacture of car, can now easily exceed £150 per hour. That covers for all the training courses mechanics have to go on in this modern day. Even then, some problem may crop up (and yours may be one) where it is not common and even manufacturers bulletins and courses are not up to date…… it happens.
Leaving your car with the dealer for a short time may be the only solution… one of the “joys” of modern day motoring.