There is no need, as players are usually too fast in relation to calendar.
Flat rate of research in buildings was unchanged, but modifiers (% things you can see in screenshots) were lowered.
That's true, but then why the buildings had the values they had, if they could be halved so easily? I mean it seems to me as a temporary quick fix. After upgrading to the latest SVN, while I no longer get overflow, my research rate has "lost" like 200000 points.
You are two and half era too fast and you didn't even conquered third of map.
I suppose it's a matter of personal preference and playing style - how quickly you expand initially, etc. In my view, it does not have to be the case that all leading civs should always be in the same era.
Hopefully @Thunderbrd can fix it in code (and perhaps just in case check for other possible overflows that could occur in late-stage game).