> just read an extra second [...] accidentally trigger watchdogs

Well, this seems to touch heavily on the concern: if your job normally takes 0.1s and costs $100, it could accidentally be considered to have taken 1.1s and therefore cost $1100. This is quite contrived, but if you consider that some people put very infrequent cron jobs at the top of the hour (which isn't typically the best idea, but I digress) and it might start just ahead of what the billing system considers to be the top of the hour, theoretically there's something to this concern.