Could happen, your toilet could over flow if it doesnt shut off too right?
Only if it's clogged. The way toilets are made they manually flush if too much water is in the bowl. So like you could just take a bucket of water and dump it in and it'll "flush" to not overflow. But the bidet just sprays water outward.
Before I moved out of Portland, there was a resident that lived above me and across the hall, and twice his bidet malfunctioned while he wasn't home and I had to go in and stop the leak and clean up all the water. It was dripping out of the ceiling right in front of my apartment.
And when I say stop the leak, I had to turn off the water supply line to the toilet.