In reality, most all tractor mount back hoe's aren't meant to pull stumps, they are meant for digging dirt and limited debris in the trench.
Of course human nature tends to cause owners to exceed the capabilities of them and then stuff fails. The primary reason I don't own one actually. I consider a tractor mounted backhoe to be one of the most expensive and useless attachments anyone can buy. If I require any digging to be done, I rent a mini-ex. While they cost a bit to rent, you are absolved of any upkeep or incurred damage for the most part.
The Kubota dealership I work at part time... It seems like every customer that purchases a new tractor wants a backhoe attachment and the owner tries to discourage them but they still insist and he provides... They use it a couple times, find out how hard they are to mount and dismount and most times wind up sitting in a corner somewhere, unused collecting cobwebs.