I don't agree that the 's' denotes the plural of mathematic. There is no such thing as a "mathematic." Similarly, the 's' on the end of "logistics" does not denote more than one logistic. These two words are nouns in their own right, not the plural form of something singular. This can be seen as they take the singular version of verbs. e.g. "Mathematics is a subject I hated at school." You don't say "Mathematics are subjects I hated at school."
Some schools of thought see "mathematics" as a "mass nouns" - these are nouns that denote an uncountable substance (e.g. water) that cannot be quantified by numbers alone. You cannot say "1 water or 2 waters", you have to say "1 litre of water or 2 litres of water".
I don't see mathematics as one of those. I see it as a singular noun in its own right that happens to end with an 's'. Since both "Maths" and the alternative "Math" are abbreviations, it's really a matter of convention as to how Mathematics is shortened. My view is that in the UK, "Maths" is the accepted convention. I know when I see "Math" I often remark "Just the one Math then?" I'm not really suggesting that Maths is a plural, just highlighting what I see as an unconventional abbreviation (which I happen to find extremely irritating) being used.