There’s a force field around Crimson Jack’s vessel and the Falcon, so no vacuum. It’s then shrunk to prevent Han from getting back to the Falcon.
IIRC, at least one fan letter mockingly called Jack’s star destroyer the metal doughnut.
A pity we didn’t see old Imperial battle wagons re-purposed as Resistance ships. I would love to see a zero gravity shootout in a SW film someday.