I grew up in an orthodox Jewish household and know lots of Jewish people, and I had to look up the term shiksa as I’d not heard it.
I can understand Joanne not knowing about Shabbat. I was more surprised that she didn’t know the charcuterie board would be a problem. And that she wouldn’t have discussed her gift with him first.
That said, being rude to guests is a big deal in Judaism and I’m annoyed at the reaction. I get that it was meant to be about Noah’s family disapproving of Joanne vs Rebecca, but it came off badly.