That explains the when, not the how For example, the reality stone that Rocket stole was a fluid they extracted from Jane. How did humans who never got to study the Reality stone or the Ether turn the Ether into the stone and back? Same with Tesseract. You think the containment thing was just some glass? To house an Infinity Stone? They broke it, that part's easy, but to return it, you'd have to put it in the Tessearct again and Captain America took the stones and not the original containers in a briefcase
He figured it out. Who cares? It's not important to any story.