The old guys saying it's pointless with today's cement reminds me of my granddad. He swore by a spoonful of sugar in his plaster mix for years, claiming it gave him more working time. Some tricks just stick around from when materials were less consistent.
I mean sugar actually does work as a retarder, it's just that modern additives are way more precise. Kinda wild that the old trick still has some real science behind it though.
And honestly, even with modern additives, sugar is still way cheaper and easier to grab when you're in a pinch. Plus it's kind of comforting knowing granddad's old trick was actually based in real chemistry, not just superstition. Have you ever tried it yourself or just heard the stories?