That'd be a plot twist
It would!
1. He isn’t shocked when she knows facts like how Alicia would be dressed, where Alicia will be, who the love interests are, etc.
2. He is the only one of all the “game” characters who noticed the purple eyes that mean royalty.
3. He repeated word for word what a female otome game character might say.
With that possible plot twist in mind I might re-read it to see if there are other clues I’ve missed. Then again I could be completely wrong .
From reading the novel to where it got translated, he's not. I think he just takes things in well cause of how Mary acts. I rather he not be reincarnated. There's too many of that one other character who is also reincarnated. I prefer him being the easy going butler that just goes with his mistress shenanigans no matter what he hears from her.
I wonder if Addie is also reincarnated. Maybe he played one of those games, but with female targets and one of them said those words he told Mary that Alicia might (and did) say. It was word for word. Hmmm.