Dutch. Not kidding. Plural of hobby is hobby’s, not hobbies for example. Same with pony’s, baby’s, lolly’s and even newer “borrowed” words from English like reply’s. We use the apostrophe and s if there is no vowel before the y.

I’m telling you it isn’t supposed to be grammatically correct. Baguette’s when pronounced sounds closer to begets than baguette. It’s also funnier (at least to most people) since it’s wrong in a comedic way.

Also, why do you think the 's is pluralizing? There’s no indication whatsoever that baguette’s is supposed to be plural.