> It’s not gross. It’s a simple solution to a simple and common cron problem

No, it's gross. By providing that facility in the wrong place it discourages implementing it in the right place to people who come at the problem from the cron perspective.

Wrap the command in a flock-running script. That script goes in the crontab entry. When you're inevitably debugging your cron-scheduled command - paydirt! The command serializes itself still while you're manually testing instead of shitting itself.