As far as I can tell, the only "hyper-technical" part is deciding what is, or is not, a fumble. That doesn't seem to have anything to do with the rule itself, since that can happen with a fumble and recovery anywhere on the field.
I'm not sure what's "unfair" about the rule. It's basic football - don't fumble, especially around either end zone. If the offense fumbles through its own end zone, it loses possession AND gives the defense two points. Why minimize the penalty for fumbling through the end zone at the other end of the field (and, indeed "penalize" the fumbling team with a relatively easy shot at 3 points if not 6?
If the touchback for fumbling through the defensive end zone is "unexpected", it's largely because fans are simply not familiar with it. However, Butler certainly was. And I certainly was.