Yes I completely agree with that, although it is diverging from the subject of approach briefings to some extent. But so what! The FMC is an abacus. It is a tool for the pilot to employ, not be employed by. Where perhaps there is a similarity, it is that the programming of the FMC should largely be completed before either of the primary briefings take place. The rest of the time there should only be regular inputs as and when time and priorities permit.
Far too many people typing away furiously (or not as the case may be) when their priority should be a timely course/ speed/ or altitude change. Or heads down doing something unnecessary when their priority should be in flying the aircraft, or monitoring the pilot who actually is.