A quick solve on the first day! I have completed the grid but ... The 2 3-letter words hidden in the grid - are they 2 animals (closely related) and in symmetrical centralish position?
I didn't see it straight away. I saw two/three 3 letter words going across one line, but then I saw the 2 mentioned above being related. I also don't see what it has to do with completing the grid the correct way as I assumed there is only one correct final grid