I have seen cleaner shrimp walk on Haddoni and Gigantea carpet without been eaten. However if the tentacles touch the body of the shrimp, he is history.
After seen these happened, IMO,I think being small and have armored, the anemone cannot stick enough to the legs and the shrimp can break free. The body of the shrimp is another mater. The larger surface area mean the anemone can really put enough stinger harpoon to the body shell. While the stingers do not harm the shrimp, unable to escape and eventually got drag to the mouth will kill the shrimp.