I do exactly that as well, Crys. There has been one instance to date where I had a weird thing happening, practically white growth on well-rooted new transplants, and I knew the coco was charged and that I was feeding at decent EC/pH levels, all within range. So I did a little searching and hit upon this method to test both parameters, I feel more accurately because I feel the results speak for themselves (i.e. I was able to solve the problem, even though I was following the guidelines you mention).
Take equal amounts of medium and 0ppm water, making sure to log pH prior to mixing (I use that PureWaterClub RO/DI 6-stage unit), mix and allow to settle for 5-10 minutes. Filter out the solids, then measure parameters.
I discovered that the coco I'd used to transplant had a very high EC and pH, likely from being allowed to dry out in between transplants. A good flush brought it back to very acceptable levels and the babies in question greened right back up and growth took off again, just like it should.