No. It isn't. I've seen it, personally, from people in my real life, in person. My mom's boyfriend, one of my sister's partners, like half the people my dad invited to his wedding. Carnists love to brag about how much meat they eat. It absolutely is performative for quite a lot of them.

I even have a theory as to why you haven't noticed it (which I admit I could be wrong about). Here's my theory: you're not vegan. Just like cis people often fail to recognize when they're performing gender, carnists often fail to realize that they eat performatively, because it's "normal" and "everyone" acts the same.