No, don't blame that on anxiety, this is not the first time he's ever had an interaction with her, he started tweaking out after "accidentally" sending the message asking about the manga chapter, which is a perfectly normal question to ask someone you've already talked to on multiple occasions
And why the hell would you assume SHE doesn't care about what he thinks, hell, why would HIS dumbass assume something like that, as if she doesn't always act like a cheerful puppy whenever she talks to him
The overreaction and thinking is completely stupid here