So, you detune the bow from shooting your broadheads perfectly to make them shoot to the same point of impact you get with field points. It's not perfectly tuned for either, but maybe good enough to suit your needs.
Tuning to shoot broadheads and field points to the same point of aim is a compromise tune, done for the sake of convenience. It's not an indicator of a perfect tune.
So this is entirely a matter of perspective? If broadhead accuracy is yourinitial goal then a person is "de-tuning a bow" if they try to get field points and broadheads to hit the same point of aim. But, if yourinitial goal is to get fieldpoints and broadheads to hit the same point of aim then detuning could refer to adjusting your bow to get the best group size for broadheads.
Is that what you are saying?