Neuro-typical isn't offensive because it points directly to the differences in the neurological makeup of individuals. No-one disputes, for example, that individuals on the autistic spectrum have a different neurological structure.
By contrast, asking if your children are "normal" isn't asking simply about the neurological structure of their brain. It covers a far wider remit, including behaviours, thoughts and feelings. As I mentioned earlier, these kinds of different behaviours may be "normal" for some individuals on the spectrum and suggesting that their emotions, thoughts and behaviours aren't normal is deeply insulting. The reason it's so insulting is that anyone who doesn't fit the "normal mould" is typically considered to be dysfunction, substandard and inferior in some way. This is how people on the spectrum have been treated for many years, and continue to battle against. This is why using the word "normal" matters.
The thing is, I totally get how you could use it accidentally and without meaning to cause offence. But having so many people here, many of whom either are on the spectrum or have children with additional needs, point out that it's offensive, it would have been nice to acknowledge that fact.
MN admin clearly thought the same as they offered OP the chance to reword her post - which she declined. That says it all really.
Just as an aside, evidence suggests that how you think of your child has an impact on your parenting. I'd suggest that you stop thinking of your child as abnormal because she is quirky about a cup. She needs your support, not to be privately judged as being weird - which is what you implied.
This is far too close to home for me, this stuff matters on a personal level. I'm out.