I've had this theory about Thailog for a while now and I'd like to share it. I think Thailog is a teenager. I know that's a bit weird but I dont think Gargoyles age or mature as humans do and I think when Sevarius aged him up he unknowingly stopped in the teen years. It's just for all his plans Thailog seems to be focused on getting Gloath's approval or acknowledgement. I know this is not exclusive to teens but I do think Thailog's lack of maturity is an indication he's not really an adult. Besides Sevarius was new to Gargoyles so he wouldn't know when they become adults, I think he just went by size.

After reading a few issues and seeing how big Brooklyn's son, is right now I think this is the case. From what I've seen Gargoyles hatch after a year and then grow faster than humans then age at a slower rate.