made a gif of this thing from the ATs manual,
Advanced Shielddropping
It is already noted before that you can drop through platforms while shielded. However, its usefulness on platforms extends beyond the convenience of falling from a shield. As explained by Isai:
“In SSB64 this is almost always the quickest way to jump from a platform (block and fall through to use your double jump instantly) therefore letting you avoid attacks that target your landing point more easily by jumping off of the platform the moment you land on it. Using this technique to use your double jump instantly from a platform (faster than pressing down + jump) gives you the height of a double jump right away which can be pretty useful when combined with attacks. So you could have the height and speed of a double jump into an upb attack as well.
lavender link jumps 5 frames before crimson link.
however, that is TAS and to get those 5 frames you'd need to input the whole shield-drop-jump in 3 frames:
1 - shield
2 - shield + down
3 - up / jump
besides that, it's only 5 frames because link takes a while before getting off the ground, if you get good characters like fox, the frame advantage is now 1, meaning, there's no frame advantage because you'll never get that sequence in 3 frames, let's be real. but you do get 1
blue frame on the shield drop.