Maybe this went a little sideways, no?
For whatever it's worth, stiffness is defined as a measure of deflection under a unit load. So, let's assume we suspend a soft and fast rod horizontally by the handle and hang the 30' of right-weight fly line from the tip. A stiffer rod would deflect less than a soft (less stiff) rod. I think we would all agree that a fast rod would bend less than a slow rod, and so a fast rod would be stiffer than a slow rod.
Now, if we take a weight and pair it with a two different stiffness springs, the combo with the stiffer spring would oscillate faster. That's why we get faster line speeds from stiffer (faster) rods. I would argue that higher linespeed would be preferable in fast-reaction situations bonefishing sometimes demands.
But, many rod decisions are highly subjective and personal. I had a whole set of T&T Horizons, but when T&T went from free warranty repairs to charging $40/per, I got such a bad feeling I did not enjoy those rods any more. I felt like I'd been had whenever I had one in my hand. So I slowly disposed of them and now use a TFO TiCr 8 wt paired with a Lamson LP 3 reel for 90% of my bonefishing. However, I'm not dogmatic about tackle; I think I can adapt to any adequate gear, l and prefer to focus on the many other aspects of bonefishing.
For instance, I'm now deeply engrossed in seasonal fly selections and going after that 'last 20%' of very picky fish that are masters of the 'cold snub' refusal.