No reason you can't do that.
I don't know that it'll cut down on cooking time all that much, the meat itself will take a certain amount of time to properly render out. You'll likely get some reduction in cook time, but not what you're thinking. In other words, if you take a 10 lb butt and cut it into 2-5 lb butts, you're not going to reduce the cooking time by half. While it is true that the mass of a piece of meat does affect how long it takes it to heat through, it has less to do with the process of rendering out connective tissue and getting to that tenderness that is pulled pork.
If you want to reduce cook time, bump up the cook temp and/or wrap in foil after you get the color you want. This will reduce the time in "the stall" and get you to tender glory quicker.
Big JT's Smokin' BBQ Competition Team
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