That's the recipe for the syrup [0], not the final beverage. The final beverage would obviously be diluted, to the given ratio of 7:1 in favor of carbonated water.
The water/sugar ratio for the OpenCola syrup is nearly 1:1, which is the same ratio as simple syrup [1].
I'm gonna poke at this only because some people take the anti-sugar message too far and use it to rationalize away the stuff that's really killing them.
Refined sugar is certainly not good for you, but a 12oz can of Coke - is 140 calories. That's about 6% of the recommended daily caloric intake.
Calories RDI is about 2000-2500 for most people. But most Americans eat more like 3000-3500 and don't exercise.
You can drink a 12 oz can of Coke every day and it's not even a blip on the radar. (A 64 oz tub of it, of course, is a different story.) What people need to do to be healthy is not overeat by 1,000 calories a day while never exercising. That combo will send you to an early grave, the can of Coke in a diet that otherwise hits the right macros, will not.
Yes, I would indeed expect that drinking around 700 fewer calories per day would lead to weight loss, because once again, despite endless protestations against the principle, calories in, calories out is the largest predictor of weight gain or loss. It's great to hear!
RDI for added sugar itself is 24-36 grams which a single 12oz can of Coke exceeds. Measuring in Calories, it's recommended to limit daily intake from added sugar to below 100-150 Calorie. [0]
% of Caloric RDI isn't the whole story. A can of Coke is less of a blip on the radar as you suggested.
No matter how bad you think artificial zero calorie sweeteners are, they are nothing compared to the damage that too much sugar does to your body.