You are of course correct, but at the same time, you might (or probably not) be surprised at the number of "system administrators" that are thrown into the job without really having the capability to expand too far on their knowledge. Having the option in cron may help those administrators that specifically search Google for cron usage, and never come across flock.

EDIT: In addition, the Task Scheduler in Windows has this type of option, so it may help those sys admins coming from that environment, leveraging their existing knowledge