My chicken... Is getting old??

Sounds like a slightly different bug to what I experienced. I had two roosters with the physical appearance of adults, yet when I hovered over them the tooltip said they were chicks. The bug in that thread seems to be animals that have the physical appearance of chicks, but the tooltip says “adult” or “elder” or whatever.

I eventually used testingcheats to delete the roosters. My single hen had recently died and I had four roosters, so I wasn’t going to get any more eggs. I deleted the glitchy roosters and bought another hen. Everything seems to be fine now.