Some machines have IDT built in, these have been developed especially so they move as fast as the foot shaft does and co-ordinate with the movement of the lower feed dogs.
With a walking foot, it is reliant on the lifting lever responding to the up & down motion of the foot shaft.
If there is any slack in time for reaction to this movement you can get a grinding of the teeth (wearing) when meeting on thinner layers of fabric. Where as with thick layers of fabric & batting, the idea is that it only assists in the movement through under the foot.
It is always best to check your machine manual or your local machine mechanic as to what is appropriate for you specific machine. After all they cost too much money to make a simple mistake that could prove costly.