Yes, so it doesn't ruin the pacing of the final section of the game. Also for the bonus area can reward people who find all the skystones. Think about it like gathering heart pieces in Legend of Zelda. It is advised you get more hearts so you could survive but isn't required.
Just a quick update on this, the new 2.0 version requires 5 fewer Skystones, to speed things up. Thank you again for your helpful insight!
For now, they have been pulled while I consider how to best add a completionist bonus . I really like your idea, so in a future release I plan to bring them back in. Speeding things up took top priority for 2.0. I played a full, regular speed playthrough after your comments and realized you were quite right, the final quest needed speeding up.