Are scratches on a MacBook covered under warranty?
Warranty generally excludes any scratches to the machine as they are normally cosmetic issue that arise from normal wear and tear as opposed to a functional defect. By extension, Apple Protection Plan will not cover it since it generally follows the warranty guidelines but for a longer time.

You could always ask for service - especially if there is some functional concern like usability or you want a second opinion if the device was made properly. I have had things covered like where a hairline crack could be something that would fail to protect the insides (on an iPhone) so it wouldn't hurt to ask even if you are aware the answer may be no.