No, is actually not true, you can create them in blueprints! You have to go to Editor Preferences>Blueprint Editor>Experimental. Its the second option that says “Enable support for TMaps and TSets.”
After you enable it, you can head back to the blueprints and create a new var. Instead of the array button next to it, its a variable icon, (the thin ovals), and clicking on it lets you choose between an array, map, or set. If you choose map, you get to choose which class is the key, and which is the value. Granted, it is in experimental for a reason. Mine crashed the first time I tried to create a map, so be cautious I guess. But it is super nice seeing that it is in there, and they do plan on fixing all of the bugs. The UI for it is very intuitive, so I can’t wait for it to be finished. I’m not sure what other bugs it as right now, but hopefully nothing data loosing.