Since one of the last updates BST got take away TH3 for 2 of it's pets.
But considering that those pets still got TH1 and are the one of the better tanking pets BST still got an unfair advantage over other pet jobs who have to sacrifice abilities for TH.

So SE - there are 2 options

#1 no TH for any pet job
#2 a basic TH for every pet job

It's up to you but I think #1 is the better option