Well, those saplings are available at /warp trade for grass. If you gave them for free to donors, it wouldn't make sense.

 

It's a nice thought but it would take the challenge away from the game. (Plus, you need 4 Dark Oak saplings minimum to grow a Dark Oak tree)

 

In all honesty. Theres no REAL challenge of getting items on multiplayer skyblock.
Sure you save up for items and spend a little cash, make some dodgy deals but people GIVE away saplings. It's not like having them in a regulated kit is gonna do any harm.

/warp grass overprices saplings anyway. 8 grass for dark oak? No thanks :lol:

 

When someone asks for a sapling I tend to give 128+ :cat

 

It might be a survival server but you can't really do much without wood.