I’ve encountered this on two planets over the past week.
I can’t find the final creature, 2-3 extinct creatures appear in the list, and after an hour of searching for a regular common always active flier, I’ll find this guy instead.
Which will be flying very low to the ground, and is very clearly one of the creature rewards from Oceanus. Scannable but not tameable or on the local creature list.
Submitted to Zendesk.
If anyone is having issues finding final creature, and suddenly has some extinct creatures appear in the list, it may be due to this. Bail on that planet and free yourself of the trouble