a coil is just that, a coil. If its parameters fall within those required by a detector, then you most certainly can use it. Obviously any chip and or coil dampening (in the coil itself) needs to be factored.
I make my own coils and what I can tell you is, there is more than just meeting the required coil inductance. When I bench test coils, I have 5 other parameters I measure, all of which impact the detector/coil combination performance. All detector designs have coil parameter sweet spots, if the coil meets this then you have an ideal world... if not then you are running the detector in either a capacitive or inductive reactactive state, on a performance front this has good and bad points but more of a concern is you can damage the detector
So with all due respect, if the TDI coil parameters meet those required by a GPX, then go for it