I appreciate your post.
My issue was you calling something marketing bollocks without substantiating your statement, which IMO was very clearly incorrect and you have now addressed. Thank you.
The GS is modeled after the B15 but it's obviously not an exact replica, moveover it's Nathan's take on that amp and it's a pedal Nathan designed to be a clean preamp and to utilise the 6SL7 tube. Before the release of this pedal ,Nathan sold a Slampegg Bee Pre. pedal, (now discontinued) that utilised a 12AX7, had a master Vol and Gain and would overdrive quite happily. Link below. All the feedback I've seen is that the GS is a major tonal upgrade and you can stick a boost of some description in front of it and the 6SL7 will break up very nicely (but that tone is not inherent in the pedal).
Slampegg Bee Pre
Peace 🕊️