In that specific example he was only talking to Aina, so I don't believe "kimono's" is being used as a plural, but as a contraction ("I was curious how the kimono's (kimono is) put together"). This also mirrors his statement earlier in the chapter.
And while we're on the subject... You don't use a dash/hyphen (-) when pluralizing a word, either. Apostrophes is the correct plural form of apostrophe. Also it's spelled curious, not curios.
If you're going to cop an attitude about the grammar of someone else's hard work in something that you're reading for free, at least make sure you know what you're talking about about first.
Yes, thank you for pointing out my own typo that I missed when typing it out. I've corrected it, as I did indeed mistype that.
Otherwise, yes, I am very much aware that apostrophes is the correct way of writing a plural - problem for you is, it wasn't a plural. I hyphenated it to specifically place emphasis on "apostrophe s" instead of just writing 's (I have not used quotation marks so that it's clearer), which clearly flew over your head.
And it seems they removed "kimono's", which was on page 1, not the page 5 usage which you seem to believe I was referring to.
And as to your unsolicited advice, I could say the same, but I would rather say that being critical of things is perfectly valid.