Anyone who has seen a picture of that drone could copy it. Heck, I bet DJI or similar could make a better version just by looking at it if they really wanted to. The drone markt is super saturated with cheap, practical components. But copying a self landing rocket is simply not possible without knowing a ton of internal details that you will never get from watching videos of it.
"Anyone who has seen a picture of that drone could copy it." and yet they bragged about taking one and reverse engineering it to make a clone.... so your saying US of A couldn't copy it by picture alone? it took them this long to get a intact one to clone?