[2021] Quick question: Trying to farm Memento

Currently backpacks are targeted loot for Capitol Hill. Doc Simpson or something appears very very early in the mission. Is it possible to just kill him, reset the mission, kill him again etc to farm the Memento on Challenging?

Seems like I'd get a lot more bosses/per minute that way than playing the mission through normally. But idk if maybe trying to cheese it like this messes with drop chances or anything? Or if exotics can only drop from final bosses maybe even?

Im kinda noob. Im SHD level 147 now and have never had an exotic drop ingame (outside of exotic caches) so im not 100% sure on their mechanics. AFAIK, and correct me if Im wrong, "generic" exotics that dont require a specific boss/mission have a 5% drop chance on Challenging from named bosses, so i dont see why this wouldnt work.