That was exactly also my thought! But when I read the following post: LINK
It said the following:
Is there going to be a tab available in the inventory/anywhere where we can monitor and view how many thralls/pets the clan owns?
Answer by devs:
Not in this patch, but we have considered doing that in the future (for example, being able to view this through the Thrall Pot and Clan UI)
So, no they do not plan to do this upon patch release 
This is also the reason I made the post. Because I assumed this speaks for itself that it has to be implemented in the same patch the thrall limit will hit.