From a maximal hydration perspective, I think you are correct that some sugar is helpful. I think for a DIY pedialite type drink this would be important.
What started this thread (3 years ago) was me trying to make a Nuun substitute, as I was using a lot of those for training indoors. This was during my ‘I don’t need nutrition on the bike’ phase, when I used just this electrolyte mix and the ‘True Lemon’ flavoring for a calorie free electrolyte drink.
I’m now more in a ‘carb the F up on the bike phase’, and add this to the gatorade + sucrose mix that Dr. Alex Harrison talks about.
From a purely practical mixing/storage perspective, I think it is easier to keep the electrolytes mixed/stored separately from the sugar even if you always use it with sugar. It gets hard to properly mix large-ish quantities of powder evenly.