I'm not OK with it.
Mint in box (or a 1:1 that says like new condition) should have no missing pieces or visible body flaws. In the 1:1 case, they could list it as excellent condition and list the scratch. In the case of missing parts on diecast, the can do the same. But not mint in box. Now the custom one should say in the title "customized" then if all else is perfect they can say mint in box and list what they customized. The car is in perfect mint condition, just customized. But even that should be in the title.