the reason the pH recommendation is different is due to availability of various nutrients in that substrate - i.e. water or ebb and flow is different from coco and from soil.
So, they'll recommend depending on what is needed - either to slow somethign down or to aid a disparity.
Regardless, your mileage will vary per seed and even more greatly in many instances by what you do to your soil over time. I always had a nitro tox with autos, so a lower pH would have helped me even in those soil grows by reducing how much nitrogen was readily usable by the plant. I use a different brand of fert and coco coir, now. So, it could be totally different.
pH is another tool in the bag. You can use it for toxicities or to improve deficiencies without adding anything of importance. Allow the plant to dictate. Use the common charts you see with pH ranges for reference on what increasing or decreasing might cause. Those charts are a little deceiving because they show different ranges -- but ranges already guesstimated and adjusted relative to that substrate, not necessarily internal to the plant.
e.g. in soil they recommend a bit higher which aids efficient nitrogen use from soil. The plant absorbs the water.. the molecules it absorbs don't change sizes. What gets through the root membrane (or simply larger openings, i don't recall) is going into the plant regardless of soil or soilless medium. the pH will inhibit or catalyze its use within the plant by either interfering with chemistry or not. On the other hand, nitrogen is much more readily useable from hydroponic nutrients and mediums. A higher pH will likely cause a toxicity of N while not being able to provide enough P and K in some instances.
So, it's not a rule.. it's a spectrum of various rates of changes of numerous factors, but you can keep it simple. Rhetorical: How's the plant doing? If you know your nutes are safe and everything else is eliminated, then you can use pH and one of those charts to adjust and see if that alleviates any minor issues you see.