I believe grid bias trem is what the Princeton Reverb uses. It doesn't use an optocoupler like the other BF/SF amps typically use. So if you know what PR trem sounds like vs. a DR or other bigger BF/SF, I'm guessing the trem in this new one should sound similar. Also, it only requires 1/2 of a preamp tube, so that would free up Fender to use the other half for some other purpose, possibly as the recovery stage for the reverb. Between that, the single channel, and the SS recto, it probably helped Fender to mimimize the # of tubes needed. That would simplify things quite a bit.