Summary:
Player in spectator mode can be slowed down by blocks that can be climbed (Vine, Twisting vines, Ladder...) It doesn't matter since in spectator mode, blocks should not stop the player.

Steps to reproduce:

1. Place the indicated blocks.
2. Switch to spectator mode (/gamemode 6).
3. Try to go down while on the placed blocks.

Observed results:
Going down the indicated blocks the player slows down in spectator mode.

Expected results:
Blocks will not slow down or stop players in Spectator Mode.