Has anyone ever tried finishing a butt in a crock pot (on low and unwrapped) vs. wrapped in oven?

...and don't forget that the true 'moisture' is minimal.  you are dealing with melted gelatin.  there's some moisture from water in the meat, sure.  same type of moisture in a piece of pork cooked to maybe 140 internal.  but in a butt, there's much less of that.  you've taken it to 200 or so, driving off much of the water.  the moisture we enjoy in pulled pork is mostly from collagen.  most of the water is gone, or shortly will be when you pull it and open it up to evaporation.

here's something most folks don't realize about 'moist heat'.  it does nothing to retain moisture.  in fact, it is easier and faster to dry out meat by boiling it (submerged in the most 'moist' environment possible), than it is to dry it out by roasting or searing at high heat.

try it some time.  boil a chicken breast until it is 190 or so.  it will be dry when you cut into it despite being submerged in water the whole time.

heating meat drives moisture from it.  you either stop heating it at a certain point to retain as much moisture as possible (130-145 for a steak, for example), or you let it go so long, somewhat slowly enough and at a gentler temp, in order to break down collagen which will make it FEEL moist, even after the water is driven off.

low and slow meat is still 'overcooked' by any definition.  but the chunk of meat used is so tough generally, that it actually becomes tender because the collagen (which held it together, making it tough in the first place) weakens and gelatinizes. bonus, that gelatin replaces the 'wet' feeling you lost by driving out most of the water.

if you'd only cooked the meat to 130-145, you'd have a truly moist piece of pork, but it would be tough.

Any time muscle is cooked, the water that is in it comes out. Items in a sous vide bag will be immersed in their own juices when removed. The advantage is that those juices can then more easily be used for a sauce. Also, any flavorings will have penetrated far into the muscle. The added advantage of sous vide is that the meat may not be taken over the temperature that destroys the natural enzymes that tenderize the meat, just as they do in dry or wet aging. Sous-vided (is that a word?) meats have an exceptional tenderness because of both the enzyme action and dissolved collagen.

The down side is that the temperature is too low for maillard reactions. I've found that placing meats in the Egg for awhile, then bagging works well. Better than searing afterwards.

To get back to the slow cooker, the problem for me is that the water transfers heat so much better than a steamy foil packet in the oven, that the protein denaturization is much more complete, and one can be left with just a mass of chewy mush sitting in a pool of diluted juice and congealing gel. Also, the only additional maillard reaction occurs where the meat is outside the water, and the escaping steam is sufficiently hot to create some of the nice browning.

For me, and oven finish is advantageous because the steam from the meat is more likely to escape, and improve the final browning.

I've always thought that about crock pot meat ... soaking in all that liquid and it was dry and chewey.

Had many an argument over that one ...