It probably means that if you use say a haste pot a second before pulling, you are able to use a second pot of some sort during the fight. They started trying to model scenerios where you can activate a trinket (say
[Mjolnir Runestone]) while where a similar trinket (say
[Grim Toll]) has yet to proc so that their procs are not overlapping each other. IE: Switch in
[Mjolnir Runestone] right before the pull. This activates it's proc. When the fight starts
[Grim Toll] procs. Now both procs are up at different intervals now and the procs are spread out instead of all at once. They are using the same concept for pots as well it seems.