Isn't an array of arrays by definition the sequential implementation?

Otherwise you would have an array of pointers to arrays. The usage (syntax) for them would be the same but the performance would not be.

They also have different uses. You would expect an array of arrays to be an array of arrays which share the same length. For an array of pointers to an array you would expect dynamic length arrays contained within the original array.

Even in c++ could you not just define some int [1000][1000]foo? I've never really used C++ but my C knowledge assumption is that is 1000000 continuous elements.