I wouldn't say this behavior is part of intelligence, it's probably the first thing nature crafted in any life form. Unfamiliarity => move.
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.