That’s probably very typical of a narcissist who posts on Facebook. They post that because they’re expecting to have their page visited by a lot of people who don’t know anything about them.
You know, on somewhat of a similar topic, I am also mystified by a mother who self-identifies as, “son or daughter’s name, mom”.
There was a talk show host that used to love to sign off her show not with her own name, but simple as “Jennie’s mom”. (Jennie not being the actual name)
I wouldn’t expect her to sign of saying, “Bill’s wife...”
She wouldn’t want to. It would make her somewhat of an appendage of Bill. Here though, she didn’t mind being an appendage of her child.
Either way is somewhat of an avoidance of being just yourself, having your own individuality.
Sure you love your kids, but some folks get so wrapped up in it they lose themselves.