I personally don't think thor's argument is ridiculous at all. The sole reason why those active frames were removed was because they didn't match the animation, and that's reasonable. It is a fact however, that one of melee link's main tools and one of the things that give him identity in that game was his nair, and he was still regarded as a mid tier at best. Thor might be putting a little too much emphasis on the exact frame data it needs, but that's understandable and it just shows drive on his part. An increase in active frames and an adjustment in the animation to show such frames, to match melee a little better, seems like relatively fair change. When you look at this game you have to remember that everyone has something good, and then they have a lot of ridiculous stuff on top of that. Just having something good makes you bad in this game. So yeah link's nair is good still, but nearly everyone else has a better one, hence he has a bad relative to everyone else.
As a side note, I don't particularly envy shadic if he's in charge of designing link, not because he's a bad guy or anything, but the fact there is an enormous amount of misinformation, and surprisingly a lot of disdain, towards link, and I could only imagine the difficulty in purposing any kind of change for link that doesn't involve a severe beating with the nerf stick