What they mean by "change the damage calculations of tanks"?

[Nektulos-Tuor]

And Tanks can absolutely be lazy without losing aggro. In Full VIT. By definition, a lazy player exerts the minimum necessary effort in order to complete a goal. Which means that they maximize efficiency. You're confusing a lack of skill with being lazy.

Being productive and performing a duty to its fullest is actually a "skill". Being able to produce more results from less by working harder is something I really love but it is something a lot of people seem to disagree with. Also cherry-picking another's phrases and words when they clearly said multiple things is rather annoying.

Situation 2: Tank A is in VIT. Tank B is in STR. They both proceed to do the exact same rotation, pressing the exact same buttons at the exact same time with exactly perfect precision. Tank A does 500 DPS. Tank B does 1000 DPS. Skill had no factor in this. Only the wonkiness of Tank Stats did..

Vitality isn't a "Tank" stat, it simply gives you more health like it does everyone else. It does not reduce your damage in any way. The way this game works is you only need enough health to "not be" one shot so your healers can keep you topped off.

Tank A in VIT pretty much means "Lazy Player." They can clearly see what the two stats do and chose the one because it makes it easier for them. When going STR makes the fight shorter and makes it easier on the entire party.