Add me to the list of people who never heard the term "chapter book" outside of Mobileread.
I have no trouble with people reading a series in whatever order they want, but I just can't do it. I've tried it. But the whole time I tried skipping around in a series that someone assured me was comprised of "stand alone" installments, I could just
sense there were tidbits and nuances that I was missing out on by skipping previous installments. And when I came to my senses, backed up to the beginning and started fresh, it turned out I was right. I WAS missing out on things, and I HAD spoiled some things in earlier installments by reading newer ones first.
So I've come to understand that those who say, "the books in this series can be read as stand alones," are really saying: 1) they don't care about missing out on subtle, over-arching tidbits that are slowly explored/revealed over the published order of an entire series. And/Or 2) that they don't notice (or don't care about) the minor spoilers that WILL happen over the course of any series read out of publication order.
So enjoy reading your series' any way you like, but stop calling non-standalone books standalones, when what you mean to say is, "I don't care about reading a series in order." There's quite a difference between the two for those who care about the little things.