In a way yes, I guess. We are both gambling and mining, only to me the difference is the approach or intent.

For example...

Intent Miner:
I'm going to mine 100 STEEM worth of SBT, as much as possible— win or lose.

Conscious Gambler:
I'm going to play SteemBet and risk 100 STEEM, hopefully I win.

It's about what your willing to risk, by setting a limit on STEEM both have lowered their risk a lot but the miner has almost 0 risk since his $STEEM is already committed to the system.

The miner is purchasing or investing 100 STEEM to the platform in return for div tokens. The gambler is having fun and entertainment at the cost of STEEM.

Also, like in Proof of Work, you won't always get the same returns while solo mining, more or less.

Just my opinion 😉