Shortly after your reply, I looked in the codex and realized there was an entry for tentacles which confirms this.

Yea, not all of them spawn a tentacle on purpose. Makes you more cautious around them, even though there might not be danger.

Marking as spoiler because tentacle.

Fixed by reloading checkpoint, just got caught way off guard by this and had to scramble to take out the rest of the demons...

Also that burrow right past it doesn't spawn a tentacle no matter how many times I reload. Is that intentional?

Explosive barrel didn't get the memo