Hi Sam,
Yes. NCrunch's implementation of MSTest is emulated rather than integrated, which means that issues like this do exist.
The tricky thing is that introducing a version of NCrunch that changes this behaviour may very well cause tests to break for other users who have written tests now relying on this behaviour. The behaviour of MSTest itself is also different between versions - In VS2012, MS rewrote the entire engine and many of the rules and edge cases are different.
I wonder if the best thing to do may be to show a warning of some kind .. I'll note this down for review.
Thanks,
Remco