I am sure they do extensive testing and don't have any issues clearing the fights
however it really rubs me the wrong way that they pretend as if the dev/tester prog experience is the same as the player prog experience
you cannot and will never convince me that dsr was cleared during testing without the use of dev tools to checkpoint each phase and prog each independently

meanwhile actual players must always go back to phase 2 each wipe.
yes, you didn't need 3rd party tools to clear dsr, you had 1st party tools that are a million times more cheaty and powerful than any 3rd party tool