Initial reports suggested Russia was recognizing the borders currently held by separatists, but even that's a grey area.

This is a very important question. These maps help to indicate the larger issue:

Donbas map 1
Ukraine

The Russian Foreign Ministry said they don't see a problem that the border issue hasn't been resolved yet and that it's not the kind of issue that can be resolved in an hour.

Even if it wanted to, Russia couldn't spell out a clear line there. Obviously, if it's 100 meters difference here and there, that can be resolved. If it's 100 km, that's a different story.