It sounds like the game is acting the way that was intended, but for a purpose that was not foreseen. Not sure I'd classify that as an exploit, and I'm fairly sure I don't even care enough to worry if it was. It's not exactly gamebreaking, especially considering how very "meh" most 15 min job abilities are.

Also, increasing the waiting period has absolutely nothing to do with this exploit and anyone who suggests it as a solution is an idiot.

That is all.