I'm the author of the original tweet, and I made a video which answers a few of these questions. https://youtu.be/OBs2-2KcN-w https://youtu.be/OBs2-2KcN-w Ess

I'm the author of the original tweet, and I made a video which answers a few of these questions. https://youtu.be/OBs2-2KcN-w https://youtu.be/OBs2-2KcN-w Essentially, the biggest issue is with spot color channels in Photoshop files. If you don't have a license for the spot color used in the file, it goes black, with no clues other than the name left behind. If you can look it up somewhere, you'll be OK, but it's a real pain.