I interpreted it as an implicit admission that they don't have any legal documentation they can use any of the old images of them, so they're hoping by sending

I interpreted it as an implicit admission that they don't have any legal documentation they can use any of the old images of them, so they're hoping by sending out mail saying "we're gonna use your photos unless we hear back from you" that most of the photographers will buckle or ignore or overlook the letter. And I've heard variations on "it won't make any [profit] so we don't think we should have to pay [you]" so many times it makes me ill.