So this is something.
This can be done with any character who has a chargeable special that can be canceled with a shield. That includes all the characters the video creator listed, and when I tested other specials, this also applies to Sonic and his Side B Spin Dash (before it can't be shield canceled), and Diddy Kong with his Peanut Popgun. However, the special move
also can't have stopgaps inbetween the charges; Pacman's Bonus Fruit, Sheik's Needles, and Donkey Kong's Giant Punch do not allow for this type of cancel. Robin's apparently an exception due to the animation itself imitating a continuous stream of energy despite having four levels.
This helps Diddy and Mario considerably, to let them control space and throw out aerials (And Monkey Flip) at a whim without needing to return to shield. Sonic gets to SH Bair out of reverse Spin Dash rather than FH them, and this helps Robin, Samus, and Miss Fit for clear reasons.