Tic Tacs get away with the same lie by counting one Tic Tac as a single serve.

Wow, I thought it was going to be less than 1, and rounded down, that's just inexcusable that they're allowed to round 4 down to 0.

Though, in practice a drink sweetened with splenda will have fewer calories than one sweetened with sugar, because you need less of it to achieve the same perceived sweetness. A single sugar packet is around 20 calories.

good video. note :if splenda has dextrose in it already then you don't need to use the invertase.
Splenda is sucralose which isn't well digested 10-30% in the gut depending on what microbes you have but it has a horrible aftertaste and so I imagine they used dextrose right up to the 5% FDA limit to help mask it.

How are these rules created, and why are people always surprised by them? I imagine there's an argument made around margin of error, and then where the line should be is lobbied for. Is the "under five equals zero" rule reasonable or shady?

I feel like I'm arguing for the five second rule.

Its called lobbying or legalised corruption. It's a very cost effective business strategy.

To play devils advocate... the average calorie intake for an adult is between 2000-3500 depending on age, gender and activity level. Let's take the low bound of 2000.

So 4 calories is 0.2% of your recommended daily calorie intake. In other words, you'd need to eat 500 packets of splenda a day to maintain your body weight (sidenote: REALLY don't do this).

Basically, when a meal is 6-800 calories, the difference between 4 and 0 is almost meaningless.

That said, saying it has ZERO calories implies that you can have as many servings as you like, which is obviously not a good idea.

In conclusion, drink your fucking coffee black. Anything else is just being a pansy.