I think the potential for unattended food in a pack without a can becomes the issue and this would be where the rub is with any ranger. While splitting a can has always worked for me, I could see where one could be busted for this. It probably has a whole lot to do with which ranger checks you and what sort of mood they’re in. Being strict on it makes sense because from their perspective, it’s probably dubious that a hiker is going to pack a bear can while stopping for a swim and leaving a pack unattended, etc.
These days I likely wouldn’t go to the trouble of splitting a can with someone unless it was one or both of my children, in which case I’d just carry all the food in the can all the time. I’ve had many group trips in which people had to split up mid-trip for various reasons and think it’s generally smarter and safer for everyone to be self-sufficient. If you’re already flirting with a 8-12 pound base weight a can is no big deal anyway.