[The Munster]

Here it's down to the Driver. Even if a member of the public approaches a Loader with something they want to dispose of outwith the wheelie-bin, the Loader points 'Joe Bloggs' in the direction of the Driver and he makes the decision then it's usually what mood the Driver is in; different in this case when you're doing a special 'green waste' uplift.
I know what you mean about wanting to get the run finished then tip as quickly as possible, been there, done that.
Newer vehicles have 'weight display' in the Cab so when you reach the max point then it's leave everything that's left and tip = having to return later.
If it's any consolation to you, here, the Loaders wouldn't have ended up 'on the mat' but the Driver would have been hammered !