very neat to see that they swim 'forward' with their tentacles grouped together as one. freaky
Ofcourse this is no proof but to me it shows some kind of intelligence.
They have advanced problem solving capabilities and a distributed nervous system that can achieve levels of parallel processing software devs dream of.
We don't need to go to other planets to find intelligent life, it is already here. We are just aren't smart enough to communicate with it yet.
I have no knowledge on how they identify/distinguish food over a rock, if the tentacles have some sort of receptors on them, but apparently this didn't "taste" like food, thus unworthy of eating or fighting for and therefore better safe than sorry.
If it doesn't move => go check it out.