[1.3.3069]Birds hatched in Pen still need wrangling

[zgrssd]

I had a nestbox with Fertilized eggs inside the pen.
The chicks hatched.

I still had to wrangle the chicks. Despite being hatched inside it, they did not count as part of the pens population.

[Pheanox]

I would need a save of this happening, if the pen is enclosed this is a bug, however I am not able to reproduce this on my own playthroughs.