This medical report is NOT at all about popcorn lung disease (bronchiolitis obliterans), rather it talks about a case of acute hypersensitivity pneumonitis, which are two very different conditions. The authors didn't present any analysis of e-liquids that were used by the patient in order to establish an actual link between diacetyl and hypersensitivity pneumonitis. But it does report that the condition fixed itself pretty quickly and the patient did not have any long-term adverse effects from the sickness--clearly indicating that this is not a brochiolitis obliterans case, because with a quick search anyone can find that brochiolitis obliterans causes irreversible damage to the lungs.
It's very disappointing that a medical journal would allow for the printing of misleading information that discusses popcorn lung disease for a patient who was not at all suffering from it and tying electronic cigarettes and vaping into it when there was no proof presented that it was what caused the patient to get sick.