>"No, I was not actually playing video games and surfing reddit the entire time! I actually wanted to invest more time in ____. Can I share with you what I learned?"

I consider this a self-reflective question on the interviewer's part. If your interview can't sniff out the gap in their experience, then there are two possibilities.

A) The most likely one: your interview sucks and you're not as good as you think you are

B) The gap doesn't matter.