I am 4.0-4.5 borderline.
What you say makes sense as less tension generates more spin as string move and snap back, but at the same time more rebound from strings so more power.
My racket is similar to a pure drive, 100 inch, 24mm beam. I use a poly/synth gut hybrid regularly and I have lowered my tension from 55 to 53, to 50 etc, and true, more spin, more snap back but more trampoline effect. There is a limit where the stringbed feels too trampoline like though.
The theory makers sense going low on gut and cross poly. But in real life situation, at least on my personal case, there was too much trampoline effect, that is why I think in my personal case a low powered cross poly would be a better idea with a 17 gut main.
Don't you think so?