This bug is a little hard to explain, so have a look here: https://gyazo.com/9649b3ada55a340796d0db0e25997e36
My tab settings for close is set to "Always activate related tab" and "Activate in recently used order". I opened each link from their own distinct pages, but I've noticed that despite the "youtu.be" tab being the lastest recently used, it'll pick the "youtube.com" one over it every time. I can't help but assume this is due to the title of the tabs, because it only happens with these links:
I hope someone can recreate it.