If KSP has taught me anything, it's that refueling in orbit allows you to increase the payload weight without needing worry about dealing with increased thrust requirements, weight related fuel requirements, then thrust, then fuel.....

By then end your rocket has gone ...

Not surprising, this has been going on for decades in NATO aligned air forces. Military aircraft regularly take off light on fuel and meet aerial refueling craft while en-route precisely to exploit Newtonian laws.