How long did you cook, and what size butt?
Temp doesn't always mean "tender". It means "done" in terms of meat temp. Depending on the thickness and size of the butts, you'll find that if you didn't cook long enough to render it down, that onces you get to the bottom middle, you will get a spot that is pretty tough, and doesn't pull.
You can cook them, and then rest them in a foil/towel/cooler combo, and it'll help. Or you can just go full crutch mode if you HAVE to have it that evening for dinner. Put it in a foil pan, add a little apple juice, and foil the butt up and put it back on your smoker/grill/etc at 250* and let it go for a couple of hours. You'll end up steaming it essentially and it'll help you make it more tender, but at the cost of the wonderful bark on the outside, and sometimes you can make the meat a bit mushy.
I've found that a 5-7 pound butt needs no less than 10 hours at 215 or so. 12 hours is ideal, and if you don't have much time, find the shortest butt possible, as that will help you overcome the stall as well I've found.
The bones should literally be about spit out from the meat when it's done. You should be able to but a BBQ glove on, pull the bone out with one hand, and smash the butt in a pan, and it come apart in strands. Pick out what larger clumps of fat remain, and you won't have much left but juicy buttery meat.