I'd say you never know your bettas true personality until they are in a tank with adequate space.
Before I knew anything about betta care I had my female in a .94g cube... Granted I knew she had personality because she would follow my finger and watch my every movement, but until I moved her into my big tank I didn't know she had long flowing fins, nor would her vibrant purple coloring have come thru. She grew a full 1/2 inch within 3 weeks. She rewards me every day with her wind sprints across the tank to greet me.
Your boy is probably just so very enthusiastic about the space he's been given. My betta is quite a comedian... It sounds like yours is too.
I also keep my betta at around 80 deg F... If I did math correct yours is around 77...?
Also, what are your parameters? Have you tested your water lately?