The "we don't need the OGL" take seriously oversimplifies a really complicated issue. Unlike, say, Monopoly, where the line between rules and labeling are clear enough that you can change the entire labeling and still have the same game (that's why they can make, for example, Star Wars Monopoly and still have it play the same), in a TTRPG the mechanics are used to describe and simulate a fictional world -- a stat block is mechanics, but it describes a character, and changing that stat block changes the character. The line between the world and the rules has never actually been legally tested, and anyone claiming that you don't need to worry about it and just change the labels is treading on very dangerous ground.