The internal timestamps are not necessarily monotone because if they were forced to be then if the single clown in front of you set the timestamp incorrectly in

The internal timestamps are not necessarily monotone because if they were forced to be then if the single clown in front of you set the timestamp incorrectly into the future you'd be forced to do so too. If you want monotone stamps from the block header timestamps you can post process them to make them monotone. ... if that kind of error would be superior for your purposes. For this discussion probably the best thing to do is ignore any non-monotone timestamps (and maybe the block before them too). Because the protocol rules don't have any strong incentives for setting the timestamps precisely they're best taken as approximate.