Job Simulator definitely expands if you have more room. It has multiple sizes, you can tell it has maxed out its area when the starting ”room" has museum displays behind you. Different games however have different needs - Job Simulator seems to want more forward-back room to max out, but a game like Super Hot seems to want more side-side room. Very, very few games have a large open area that can handle however a large an area you have.
They put limits around you, such as Job Simulator which surrounds you with cabinets and walls and stuff. Sure, you can theoretically just keep walking through walls, but that's not the same thing as a game supporting a larger area. Heck, Elite Dangerous, a sit-down single-position game, you could theoretically walk outside your ship (in space) and see it from the outside, but that's definitely not a valid gameplay motion.