The meta-mathematical assumptions (axioms) are the context.
Different axioms produce different truths; or if you want - they produce different Mathematical universes [1].
Maths is relative like Physics is relative - it depends on your frame of reference [2].
I'd put that in a different way: the point of maths is not really being context-independent, but to make it very clear what is the context. So, let us consider a statement A which is true provided that a certain set of hypotheses B is true. You might either consider that "A is true in the context of B" (what is commonly written as "B |- A"), so you have a context (but it is very clearly stated what it is). Or you can (often) write it as an implication: "B -> A". The whole sentence "B -> A" is an absolute, it has no context any more, because the context has been absorbed in the antecedent.
(yes, I know I am oversimplifying something, take this at the "philosophical" level)
From the lens of the Curry-Howard isomorphism where logic, category theory and type theory are just different perspectives on the same sort of mental human activity...
Implication (logic) is the same thing as internal hom (Category theory); or Function type (type theory).
It is just syntax. B |- A in logic translates to f::B -> A in Haskell.
Yeah, context-dependence is a matter of degree. However, if you rephrase the article in terms of drastically reducing context dependence, particularly eliminating physical circumstance from the context, it still says something mostly true and important.
Yeah, but it's genuinely remarkable that a solution should ever be applicable to more than one problem, other than where it was first devised. It's easy to be numb to that if you've grown up with math showing up all over the place, but that's what the "unreasonable effectiveness" thing is all about.
(yes, I know I am oversimplifying something, take this at the "philosophical" level)