Isn't it the same all over, like the way a Casino will ban a card counter when actually that is a skill. Funny isn't it, a game fixed in such a way the house wins cries foul when due to their poor coding and lack of testing they have the tables turned on them.
Like you say its not a hack, it was gaming of the system and to some may be a step too far in their morals, viz a viz the under arm bowl by Australia to win a test, perfectly acceptable under the rules but roundly condemned throughout the world of cricket.
Personally I think its fine to try to find errors in a system, I would do the same but after verifying the exploit I would have contacted them to fix it and negotiated a fee for the work done that they never did, in this case like keep half, though given the price of Steem its close to $500 which I would imagine most bounties would be around about at.
Since he has been given 2 Million tokens (approx 220 Steem) I guess it all worked out well in the end. Add that to the post earnings and everyone is probably happy now.