Mountain out of a mole hill.
If I get a pimple in just the right place, I sill don't have three nipples.
From memory alpha.
Story arcs are story lines in Star Trek that are told over the course of multiple episodes. They are not simply two-parters or recurring characters and themes, but rather plots that are interwoven with other arcs and plot threads. An example of this is Deep Space Nine's introduction of the Dominion and the eventual Dominion War. Story arcs often take precedence over other plot elements and consume a series for several consecutive episodes, but in many cases (such as the Dominion War) they may take a back seat and re-enter the picture later on.
Part two of the arc is Futures End part 2. Part two of the arc is therefore the same "story" as part one, and therefore a cheat.
3 episodes is minimum, but still that's a bullshit pisspoor arc imho.