I agree. This depends on airline and airport. For example, NH can do pre-boarding for pax "who need assistance" first on their 777-300s at LAX. Then they will board everyone at once through one boarding bridge. FAs at the a/c entrance door will not check boarding passes to direct pax to their seats. NH pax just scatter! Only a sign/diagram near the door will explain the seat alphabet system associated with aisle. OTOH, LH will board 2 classes simultaneously through two boarding bridges onto an Airbus A321 at MUC. Very efficient boarding and deplaning!