In the rules it doesn't specify that you have to end the game with 2-4 players

It does not. Because you don't. As long as there are two or more people involved in the run, it counts as Co-op.

Yeah like in old Ro-Bank speedruns where someone would glitch into the safe and trow bags outside while the other one would awnser the phone and put the bags in van, then the person inside the safe would leave the game