When he bought the original game and the 30 days that came with it, that means that he bought access to it for those 30 days. How much of that time he actually made use of it was up to him. There's always a wide range of how much time different people play. SE doesn't charge more to the hardcore and out-of-work players who spend all day every day in the game than they do to casual players who can only log in for a little while on weekends. SE charges by the month, not by the minute.
I'm sorry your friend had a bad experience at the time. I wasn't on the original game, so don't know how it was (though I'm really liking the current one). I don't really see, however, how that could be turned into a reason to get free time now. He bought a month's worth and he had a month's worth. (He just didn't make much use of it.)
I know some game companies occasionally offer free welcome-back weekends when former players are allowed to access the game again for a couple days without a current subscription. It's a type of special promotion designed to draw some of them back into the game. Perhaps SE will do the same at some point and your friend could try it then. But promotions like that are for anyone who used to subscribe and doesn't any more. There wouldn't be any special rules for people who only logged on a certain amount of time during their previous subscriptions.
p.s. Was it the game itself that was so bad or the service? ARR had a really bad week or two when it first launched, with lots of server stability issues, but they fixed those. (Too bad they didn't have them fixed before release.) A lot of us liked the gameplay itself well enough (when we could actually manage to get logged in) that we stuck it out, but I still wonder how many players they lost who would have liked the game but didn't have the patience to put up with their launch-day service levels.