thanks for the info., I didn't know when it started, but either way, it sounds wrong... pretty sure it wouldn't affect most recipes to use only one kind of sugar
Different sugars affect properties like texture and moisture retention differently, and aren't equivalently sweet.
Do you have a concrete example for the moisture retention case?
Cookies? Swap brown for white in a recipe and you'll wind up with a wildly different product, and they're 95% the same (white is almost pure sucrose, brown has a small amount of fructose and other traces).
Syrups contain quite a bit of water, and differ a bunch in constituent sugars.