A-ha! so that was you! I knew it! there’s like 3 French users on the whole board. (ok, silly joke. serious now)
As you say, law of large numbers, which is also how a lot of scams work. The submissions, I assume, must be partly automatic, so the wasted time may not be that large, possibly less than making sure the spam gets posted to the correct board.
These days there’s also a number of clinically dead forums around, with no moderation, which have turned into cemeteries of sorts, overrun by the spam-grass.