I guess I'm not following how they are unrelated. To really stress a system and find bugs, shouldn't you be putting it under realistic usage and load? In my mind using test data that closely matches real data is desirable for development purposes. I suppose I'm now actually disagreeing with the OP's statement -- that example was a specific circumstance where perhaps more care should've been taken, but for the general case I think it's actually desirable to use realistic data.

Plus I just think it'd be cool if you could use the same service/API for both use cases.