As you read more,you'll see that doneness/tender is not a linear line from cooker temp/weight/internal temp.
Think about a 1/2" slice, all across a large butt,seared in a 375º frypan,one minute on each side,to an internal of 200º.
You'd be lucky to cut it with a sharp knife,much less pull,or shred with a couple forks.
A couple hrs/lb might be more likely in 7-8 lb butts.
Just a couple thoughts.