Originally Posted by kanisatha
It is this double standard that I am questioning.

That isn't a double standard. Adding a turn based mode to a RTwP system is essentially automatically pausing and managing when NPCs can act. It may not be possible to add real time to a system designed from the start as turn based, and if there are no fundamental blockers (there would need to a system added to handle interrupting actions, etc), there would still be issue that would need to be addressed (for example, all animations and skill effects, etc, may need to be adjusted, since their time could suddenly impact balance where it isn't a factor in turn based).
There may be time based mechanics it would be difficult or impossible to cut up into discrete turns, but in general adding turn based to a real time system is a lot easier than the other way around (depending on the details of the design).