For me GTG and easy strength are the same principle, the difference being the time between sets
I suppose there is something to be said about this. Some food for thought, I hope.
I, personally, am most thoroughly steeped in Strong Endurance training principles. I have read, and re-read the Strong Endurance manual many times. And I have at least sampled from each of the provided templates provided; and have mostly trained S&S, and Q&D, across my few years of training.
In general, there are a couple of factors that I believe find some kind of similarity to most programming, as far as I can tell.
Challenging and do-able.
To pose an analogy: In musical performance, the greatest experiences I've been a part of are where the performance lives in the overlap of a hypothetical Venn diagram comprised of the following two circles: (Narcissistic OverConfidence, and Crippling Insecurity). For me, the overlap between challenging and doable is where I want my training to be loaded. I have to at least visit a range of difficulty that causes me to have at least a slight doubt about whether I'll complete the sets and reps involved. I have to investigate those limits from time to time. Or, there is a similar effect from completing a workload that seems to be a lot, and never thinking that it'll become easy feeling, and watching, over time, as the workload becomes easier and easier, till it's hard to notice.
Relatively difficult loading, and relatively complete recovery.
This is a theme I've begun to notice in a lot of disparately targeted training goals. everyone seems to be trying to find a sweet spot of loading that gets the stressors sufficiently high enough to matter, and to allow the muscles to recover sufficiently. The big differences in opinion seem to be guided by what is regarded as Sufficient; relative to the goals of training, or the targeted adaptation. Strong Endurance has very different opinions about what sets, reps, and rest are required versus other programs aimed at maximal hypertrophy or maximal cardio; for example. While they have said differences, one can not avoid the basic framework: enough work to get the body to adapt, enough rest and recovery for the body to be able to trigger more of those adaptations.
I think in these broad terms GTG, Strong Endurance, and Easy Strength (and many other programs) have meaningful similarities. But, the devil is in the details. Other (more specific) levels of analysis belie the idea that these programs are sufficiently similar to be regarded as in the same vein of pursuit. Their designs have certain features that distinguish themselves from each other taxonomically. If you zoom out enough:
training is just training. when you zoom in
some training is completely different from other training.
Insofar as I espouse that
the devil is in the details, it is for this reason that I would advocate: when one takes up a program they should do their level best to follow it to a T. I have muddied the water for myself a couple times, and I would argue that it made it harder for me to look back and learn from that training cycle. the more I changed tweaked and adjusted, the less clear it was that a given factor effected a certain outcome.