Yep, and that’s an intentional choice, according to Sage Advice. In D&D lore, druids use leather or hide armor, or armor made with special materials like darkwood or dragon scales. But, if a PC druid dons metal armor they’re proficient with, there’s no mechanical consequence for doing so, and nothing will break as a result. Some DMs might want to impose some sort of story or social consequences - maybe the Druid’s order will banish them if they find out or something. But mechanically? Nothing prevents it, and there’s no exploit the restriction is meant to circumvent.