Someone who actually has a G-Major might post.

Typically...yes.

It all has to do with the effects input and output impedance, how it handles the signal strength coming form the amp and how the amp handles the signal strength from the G-Major.

All the "interrupt FX loop" does is allow you is insert devices in series between the preamp the phase inverter in an amp that was not designed or tuned for such a purpose. 

Not familiar enough with either to give advice.  But, in theory, the best buffer,won't have a tone but be transparent, they aren't gain stages or a tone stack or a boost, they are just there to make everything simpatico between the amp and effects.