If it clogs, it could overflow. One hypothetical I am thinking of is if something big like a piece of algae gets stuck in the filter roller when it is at the end of the roll and there is no more roll to go out, then it would change flow rate. Take that to an extreme and you have a flood. Note that I haven't played with one and have only seen lots of pictures of how they work.
There's a large cutout allowing water to safely pass through the system in the event of a clog/malfunction. My water level sensor has stuck a couple times and this has happened. It's basically the same exact scenario as disabling the machine itself - so shouldn't be any harm.
Appreciate the feedback though. My primary concern is that my in-laws will be house-sitting for us...and (don't tell my wife) can't be trusted to do any troubleshooting or likely even feed the correct amounts. So I just worry about some serious overfeeding and a major nutrient spike without the safety of a filter roll!
Not the end of the world but it's a new setup so I'm trying to be as stable and careful as possible in these early days before everything is super established.