I know how to apply a rule of thumb from prior statements I see, which are close to yours (ive seen 1.9) , the point of this article is "we need more" but the summary didn't say what "more" was.
So where does your 2.2 come from and how does it adjust with age?
In any case going beyond 2.2g/kg/day is almost always overkill and wont help, but reaching that amount is beneficial at every age, and more important at old age.