Here’s the thread referenced, BTW:
Appears to be more of British usage, just like “abattoir.” The only reason I know the word “abattoir” is when I lived in Hungary, our band used to practice in what my friend from Cambridge, UK, called an “abattoir.” I was like, oh, you mean a “slaughterhouse”? I will admit that “abbatoir” is a far prettier word for it. I would similarly not expect words like “courgette” and “aubergine” to be accepted in the Spelling Bee but who knows.