I absolutely agree that, tagged or not, there is no certainty at all that, as a premium pax, your bag will be one of the first onto the belt.
Even where baggage is handled by BA staff, it is a bit of a lottery. Where handling agents are involved, even more so, no matter the details of the service level agreement.
It takes a bit more time, and requires a bit more organisation, which means it costs more money. QED.