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Literally anything that is genuinely a plural will add an -s to the shortened form. Even heard someone shorten Timberlands to Timbs once (as in the shoes). Obviously we call all agree that person was a wanker.
The question is whether mathematics is a plural in the first place, and like most linguistics, it's full of people trying to 'logically' prove that their preferred way of saying something is 'correct' when there's no such thing as correct, just common.
Having said that, I'm not going to take any lectures from Americans on the use of plurals, when they can't even decide within a single sentence whether something is a singular or plural. "Man City is playing much better than they were in the first half." Fuck off.