Tough to tell. There is a bit of rolling at the spine which would pull the cover in past the pages, but who knows?
I've trimmed Sunday comic pages from newspaper sections enough to know that even a sharp razor can catch a few "pills" or crumbs of paper and result in small tears as the blade plows through more than cuts the newsprint. A few of those "nicks" look suspicious on your right-hand edge, but I've seen them result from factory trimming, so again, it seems inconclusive.
I feel the more you wonder about trimming, the more likely you are to talk yourself into the opinion that a book has been trimmed. I've gone through it myself.