pH pot culture should be slightly higher than hydro. 6.2 to 6.6 that product may be at 6.4 to 6.6. Nevertheless buffering peatmoss is a hit and miss proposition even with the manufacturer. Many factors can affect the pH outcome right down to the size and surface structure of the added limestone.
Most cheap soil pH meters aren't worth buying, I've never seen a valid reading on any of them, but some do work. Water pH matters, it's more common it to be over 7 because counties put phosphates in it to protect their pipes not to mention floride. Putting all the perimeters to perfection isn't always possible.