Every time the issue of supermarket-chemistry comes up, there's bound to be someone to raise their finger stating that people shouldn't be doing it, you're running all manner of risks, things might go wrong, blah blah blah. In reality, the stuff of course works just fine.
I have never said you shouldn't use grocery store and home center products for photographic purposes
if you are careful not to obtain such products that contain extraneous ingredients which may have an impact on you results. What I have expressed is that I don't understand the attraction for doing so. You have mentioned convenience. I suppose cost is another. Yet there seems to be something else at play.
One reason something else seems at play is that I frequently see threads asking what is the best camera, what is the best lens, what is the best camera bag, etc., and those threads are juxtaposed with threads asking what is the cheapest film, what is the cheapest enlarging paper, what are the cheapest processing chemicals, etc.. I guess if you are vigilant about getting the cheapest materials, then you can afford the best equipment, but the two don't seem to go hand in hand. And then there are those prefer old folders, expired film and paper, and processing chemicals from grocery stores and home centers, and the end results appear to be beside the point. Seems more like a lifestyle choice than anything. I don't shoot Leica or Hasselblad, but I do use the best materials I can afford. All different aspects to the hobby I guess.