It's an abbreviation, not an attempt to make it singular.
In that case you are correct, you can turn it into whatever you want.
However, it's widely accepted in England as "Maths". If in America, which is where i believe the phrase "math" came from, they want to abbreviate it like that then they can suck my balls.
I've never met a human who calls it "Math" by the way
It's American s**** which is slowly creeping in to our language.
Others that really irritate me are counter being used instead of un- as in counter-productive or unproductive, two times instead of twice and marquee signing. I mean wtf is a marquee signing? It has no equivalent in British English. Wankers
They both have different meanings though
Or atleast that's how I see it