Should it not be " ... trying to stick its
tentacle up me"?
Well, after a quick Google search, I'm even more confused ...
"
Barring a few exceptions, octopuses have eight arms and no tentacles, while squid and cuttlefish have eight arms (or two "legs" and six "arms") and two tentacles."
"Octopuses have six arms and two legs, not eight tentacles as they are sometimes mistakenly called."
... So, do alien monsters have limbs, or tentacles? Who knows, I guess the main take is ... don't overthink a VN, it uses blood and resources in your brain, that could be used better elsewhere.