Thanks for reaching out. I confirmed with the team that Hair must be submitted as a rigid accessory. The reason why there are mentions about hair in the layered accessory docs is because there are some older layerable hair assets uploaded by Roblox some time ago.
Since the layerable hair isn’t a possible user-generated Marketplace asset, I added an update to the layered accessory docs to remove mentions of hair. This should be live in our next docs publish.
Sorry about the confusion! I appreciate the report to help make sure our docs are accurate. Have a great rest of your week!
naahchos