Your teacher is correct, here is a good reference – http://blog.darrenstokes.com/2009/03/30/watch-out-for-those-waitone-overloads-when-you-need-backwards-compatibility/
To be honest I have never heard of this before and the above article does not make it clear whether the issue is automatically resolved at compile time. It seems like a relatively easy fix, I’ll add a bug report for it and will fix in the future.
Regards,
Marc