Good question. I think initially he was being a rebel of sorts with the mentality of "I'm doing something everyone else does behind closed doors even if it's illegal...and you can't stop me". He's been talking about how it should be legal for so long, then once it actually happened he was so elated, and his enthusiasm went overboard.
My guess is because this was his first acting job. And not just because he looked like a young Tony, but because he got the voice and mannerisms down pat too. For someone who just entered/started his acting career, I thought he did an excellent job.
Maybe they resemble one another physically, but I'm sure their personalities must be different...otherwise, what's the point? Based on what we've seen so far, Heather appears to be a lot more affectionate and so far, no eye rolling 😉