It's pretty minor (stuff like a t-shirt with the Galaxy logo on it) but it's kind of annoying that it's locked.

It's a few cosmetics and some "pre-order" style weapons that are references to Witcher. Nothing substantial. There have been mods to unlock them without Galaxy since forever, and despite all the improvements, CP2077 still benefits greatly from some mods. You're really shooting yourself in the foot playing vanilla.