That doesn't follow? If you replaced every call of memcpy with memmove (to use an example from the standard library), then your program is no less correct than it was before (and possibly more). The converse is that adding "restrict" qualifiers to existing functions can only make your program less correct, not more.

In this context it follows. If you believe the pointers dont alias (and want to use simd) then there should be no data-dependencies inbetween indices. (If there are data-dependencies it is quite likely that you have designed your algorithm to accomodate that, i.e. make it suitable for vectorised access. parallel prefix-sum would be an example of this). And without data-dependencies vectorized code is exactly equal to unvectorized code in all circumstances. If however, you do have data-dependencies, then your algorithm is wrong. Vectorizing can surface this error, while keeping it unvectorized may hide it. In my previous example (parallel prefix-sum) if you had a direct data-dependency to the previous index your program would've been wrong - regardless of vectorization.

In short, while your statement is true in general, I believe that it is not applicable in the context of the discussion.