L cancelling is not a bug, it is an altered feature from smash 64, where it was called Z-cancelling and removed all of the lag from aerial attacks. I also have a hard time to believe, that wavedashing is a bug, as they specificlly implemented a state transition for wavelanding (hitting the ground while in the airdodge animation), it is more a clever exploitation of this mechanic by jumping and immediatly airdodging into the ground, thus carrying over a whole lot of momentum.