What would you do ?? ...

.... If you're SO gets annoyed with your mother. My mother has this thing that she does where she talks in a really sweet and light voice. She does it with us in the house pretty often so it's just a cute habit that we've lived with over the years. Well, My SO mentioned it once saying my mom acts likes she's a little girl. No big deal. My mother naturally likes to make people feel welcomed and she goes to give him hugs. Then he hesitates to do so like he's annoyed with her. I asked him about it and he mentioned how it's uncomfortable for him when new people come in his personal space and he's caught off guard. He said he has to get used to my mom just giving him hugs. She treats him like he's a member of the family. That's how she treats all of my friends especially somebody I'm dating seriously. It's just alarming to me that he wouldn't feel comfortable. It's been a year. It translates to me that he doesn't take me seriously enough to want to build a connection with my mother. I know he's in a relationship with me but if you were really interested in someone, wouldn't you appreciate their parents welcoming you rather than being annoyed by it. ? It makes me wonder if he sees a future with me because we would all be family if he did. Why would he feel so uncomfortable if all she does is speak and give him a hug if he takes me seriously? Am I overreacting?