https://www.youtube.com/watch?v=LmhRiG4cC-U
Search YouTube for opening amiibos and you'll find many more videos, but this one doesn't seem to damage any of the plastic in the process. I don't think it would be impossible to carefully cut as per the above video, and then re-glue with a light coat of super glue or something. The chances of there being some visible evidence of tampering in that case is likely pretty high though. Then there's the separate matter of modifying the Samus figure.
As far as my opinion, I'd prefer to reserve judgment until I see more photos. Cuz like I said it is still definitely possible those marks are just glare. Hold one of your amiibos under a lamp and you'll see what I'm talking about.