Would you see this as inappropriate/wrong?

Imagine your mother has been dating a guy for < 8 months. The guy has a daughter who a few days ago gave birth to her first child. Your mother makes a post on social media with photos of her and the guy she's dating holding said baby with a caption that says "we have a little grandbaby". She's now getting congratulation comments for becoming a grandmother...

Thoughts? Feelings?

Am I alone in thinking this is incredibly weird and not okay?

Updates
+1 y
I feel like I should add that this is about my partners mother, whom he doesn't currently talk to. Since this has happened she's made a few cryptic posts pertaining to the lack of relationship. She's a very impulsive person. Has jumped from relationship to relationship has even married a guy after knowing him for 6 months then divorced less than a year later. She gets upset about nothing and says hurtful things then act like nothing ever happened.
Would you see this as inappropriate/wrong?
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