Well, it's Neon's character, so however Mason acts is technically in-character

But, it didn't feel out of character, to me. Just felt like we're getting to know things about the LI.
Reminds me of how people also thought Viola might be acting out of character in the clothing store, but.. you could pretty easily chalk it up to her being more comfortable around the MC after he helps her, and stepping outside of her timid shell; or just being more comfortable in general when she doesn't have to worry about her disgusting landlord anymore. Maybe the author wasn't planning some of this when he first wrote the characters, but as long as you can comfortably reach for a satisfying explanation, and as long as it's internally consistent with the character he's written thus far, I think it works. When we can't do either of those things is when we have a problem.