At least it was a positive misinterpretation! It wouldn't do for Kai to think he's somehow unhappy with this outcome! In fact, such an honest reply nets a nice, soft smile from Shinji. So it really is just a coincidence? He's not missing anything big and important, and Kai hadn't felt the need to make a big deal out of today specifically. That's pretty reassuring.

"This is all really nice, so I just wasn't sure if there was something I was missing," which is true! Even if it's not the only reason he'd asked. "If you just felt like doing it, then that's enough of a reason."