Well currently in the X-Terra line the X50, X70, X305, X505, X705 all can operate at 18.75kHz with a wide variety of coils. There are several other high gain detectors that operate in the same area, Tesoro Tejon, Troy X5, White's V3, XP etc. So there is really nothing new about the use of the frequency for a variety of tasks.
As far as claims to the "same depth" as the Gold Bug II is really pretty meaningless, because the Gold Bug II is up in the 70kHz region. And as I far as I know the new Gold Bug has not even been released in order to make comparisons. And depth on what type of target in what type of ground should be the first question asked.
The only thing I can guarantee you is that if you point out any shortcomings of that detector, that the National Sales Manager & Chief Engineer will be on these forums berating you for doing so. Of the major manufacturers only First Texas finds the need to continually be defending their product quality and repair services online. They should include that fact in their Spec sheets, as it is obviously a "benefit" missing from the Garrett, Minelab, Tesoro, & White's product prospectuses.
HH
BarnacleBill