In many cases, the design effort moves from making the structure to writing out all the possible structure constraints the design needs to satisfy.
PS. This is not new at all if you look at the literature.
I.e. computers are already used for ingenious solutions and that's really all that matters here.
To say humans have no place in this is the same as saying in the future, my compiler will be so smart human programmers won't be necessary.
Frankly that design is cool but not mind blowing. If you knew how much angst computer optimization packages can put you through, you might be more cynical. Even before NNs were all the rage there were (ex: genetic techniques, hill-climbing, simulated annealing, Monte-Carlo, pick-your-optimization-technique) to do exactly the things which that Twitter post referenced.
1) AI is not there
2) Human ingenuity is necessary.
With regards to 1) of course it's not there yet. But the progress is astounding and quite a few things will be possible even before we get to strong AI.
With regards to 2) already today there are several areas where technology is better than humans to detect mistakes. In fact we use computers in many cases to test our work. This is an increasing trend and will result in end to end computer design and implemented solutions.
Strong AI is not coming anytime soon. People will still be necessary.