It does say on the screenshot the $25 option completes both ARR and Heavensward.
It will be curious to see what the next potion is. Will they make it $18 for ARR + HW and $25 for ARR + HW + SB or will there be a third tier?
I think they want to keep them separate so players can choose since some may want to skip ARR but play HW story and then play or skip SB. Hard to say the best route in that regard.
Question for any who know - if you use a story skip potion, the MSQ is flagged as completed so the quests don't show up anymore, right?
That might be a solution Square could explore. Find a way to let players buy an MSQ skip potion, a level boost potion, but keep MSQ quest chain open for play. That way players could be at current content and able to play with friends for endgame type stuff while going back and playing through the story at their leisure. Maybe that's the purpose of the MSQ "New Game+" they're talking about?