That assumes that they do actually believe it's a mistake. They didn't explain the reasons they've gone for this architecture in much/any detail. I'd be interested in hearing them talk more about that in the future.

Perhaps you or I would make a different decision based on the aims that lead them there. But there isn't enough information to say whether or not their decision was a mistake, even if it has lead to a peculiar bug. It may be perfectly legitimate and we just don't know some of the constraints they had.