This is how I feel when I hear or see people use the word “maths”, but I simply accept the cultural differences in language.
Though I don’t think throwing an “s” on a word to make it plural, even if technically incorrect, is on the same level as “basgetti”. Adding an “s” to words to make them plural, is generally a good rule, there are just some exceptions, and not that many people are deep enough into Lego to know it’s one of those exceptions.
Its like a whole country called spaghetti "basgetti" as kids and just went with it.