First one, tightly wrapped will "extend" the cooking time if done right after it comes off the cooker......
Loose tenting allows the cooking to slow at a slower rate so the whole piece cools more evenly, not just the outer edges....
Tight wrap contains the moisture, or confines it just to the piece....in other words, it's not letting the moisture evaporate off into the air (or "outer" space), but it's real good idea to let it sit open for 10~20 minutes to "stall" the cooking some, otherwise, yes, it will continue to cook until the temp drops below a certain level.....
To be more clear, when I say wrap, for me, it's almost always AFTER it's done & off pit.....wrap to rest.....two times I can think of in years where pork butt was wrapped on cooker.....a recent speed up to be done sooner (that will speed the cooking...it's why ribs can turn to mush if left too long in foil) & another where it came pretty much straight from the freezer...that was a pretty much finished cooked one that didn't get served & was frozen in foil.....
Add a bit of liquid, start heating, as it softens, more liquid, as it softens more, start to shread out with small amounts of liquid, just enough to keep the moisture up.....
Warming up.....
Panned....
Pulled out.....almost complete.....
Always have some 'Turds on hand in case thing don't go as planned....