This popular article reports a recent result in reverse mathematics, showing that a certain theorem in Ramsey theory is provable from RCA$_0$, the base theory in SOSOA. Then there are a bunch of surprised remarks, since (according to the article) the theorem itself is infinitary. Does that just mean that it uses unbounded quantifiers, or maybe that it refers to infinite sets? Isn't that the whole point of second-order arithmetic? And aren't there tons of theorems of the same sort? I don't know much about the subject, but I thought one of the basic discoveries in RM was that lots of the familiar results of calculus and analysis can be reached from RCA$_0$.

I get that $RT^2_2$ has a Friedman-like flavour that sounds like it might need strong axioms to prove, and I get that proving its strength (that was lower than expected) was difficult, but I'm having trouble understanding why there is such excitement over this, or what far-reaching consequences it's supposed to have. I'd appreciate any enlightenment.