I believe that the spider game mode is supposed to have a slightly smaller hitbox.
GD
Web Dashers
Both screenshots are taken at the same place in Fingerdash (39%), so the blocks below should be exactly the same size and can be used as reference.
You can see that the spider hitbox on GD is a bit smaller than the block while the one on Web Dashers is the same size as the block.
I believe that the spider game mode is supposed to have a slightly smaller hitbox.
GD
Web Dashers
Both screenshots are taken at the same place in Fingerdash (39%), so the blocks below should be exactly the same size and can be used as reference.
You can see that the spider hitbox on GD is a bit smaller than the block while the one on Web Dashers is the same size as the block.