It's actually not inaccurate. Last post: "General phpBB development discussion" by Johnny, Today 12:52 pm." This simply means that Johnny made a contribution to the topic at 12:52 pm. Yes, it's missing information about whether Johnny was the OP or not, but that information does not belong on the index page anyway.
Just because the name of that column is "Last post" does not mean that you necessarily have to display the subject of the post instead of the subject of the topic. This is just a hack after all, and by implementing this feature we are essentially emulating other forum software (I just confirmed by quickly scanning vBulletin, XenForo, IPB, and myBB) none of which have any Re:'s in their board indexes.
I don't want to get into whether post titles generally are necessary at all (I believe they are completely unnecessary--OK, I got into it), because I'm sure there's an RFC somewhere to kill it and lots of arguing.
But the main point is that all these Re:'s on the index page are just litter--they are unsightly, look strange, and are bad for SEO.