Having been an Ansi C programmer for a few years and having to write cross platform code to various platforms including the intresting Microsoft variation of Ansi C.
I understand the reasons why Microsoft feel that they need to do this. But, if they are saying that you cannot get your app certified while using memcpy() then, in my opinion, they should drop their claims to be ansi compatible. This will require yet another macro to mangle the calling of another function that Microsoft have changed or failed to accurately implement.
They are, again, fixing the symptom and not the fault. Maybe they should look at fixing faults properly and not the symptoms.
I also wonder if this will also impact the performance of the same code running under Windows based against the Unix's and Linux's of this world.
This would seem to push High End Apps back to the Unix like Platforms again.