YOU do the comparison:
No situation is exactly the same as any other. Some motorcycles can be over-loaded WITHOUT any luggage being involved-
At other times, its an excess (or improper distribution) luggage load involved-
And to those who question whether a motorcycle can stop under heavy braking while towing . . . . I can testify to braking so hard that the ABS intervened when almost missing a turnoff while towing my trailer and kayak.
In addition, I would NEVER tow without attaching the safety chains. The vehicle operator is responsible for WHERE his trailer ends up. A well behaved trailer with its coupling unattached behaves quite similar to a rear flat on a solo.