Blaise,
the reason that there is so much confusion is because the terms “G-scale” and “G-gauge” are usually used as generic terms meaning “anything that runs on 45mm track”…
this is bad, incorrect, and very unhelpful.
as others have said, the use of the letter “G” when talking about model trains should ONLY be used to refer to the scale of 1/22.5, nothing else.
but sadly, it is used for much more than 1/22.5.
a “scale name” should tell you both the scale of the models, and the track gauge,
some “scale names” that work well, and are unambigious are:
HO scale - 1/87 scale trains running on 16.5mm gauge rails (for standard gauge.)
HOn3 - also “HO scale”…the scale is the same, 1/87, but the gauge is now 10.5mm, to represent 3’ gauge prototypes. the “HO” tells us its “HO scale”…the “n” stands for “narrow gauge” and the “3” stands for “3-foot gauge prototypes”
HOn2 - still HO scale, 1/87, now the gauge of the model track is a mere 7mm.
to represent 2-foot gauge prototypes in HO scale.
S scale - 1/64 scale models, standard gauge prototypes, 22.4mm track.
Sn2 - a common scale for modeling Maine 2-footers.
still “S-scale”, still 1/64, but rails are now 9.5mm apart, to represent 2-foot prototypes in S scale.
On30 - “O-scale”, 1/48 scale, narrow gauge, 30" prototype track gauge.
model track is supposed to be 15.8mm…but hey! HO scale track is very close to that, so On30 modelers just use HO scale track…
etc etc.
(this list is no where near complete…its just an example)
notice the one thing these scales have in common…the scale is constant, the gauge changes…(just like in real life.)
HO
HOn3
HOn2
all are HO scale, all are 1/87.
the gauge of the model track gets narrower as you go from HO to HOn3 to HOn2…
this is all good, this is all logical.
our “G-scale” trains dont do this!!