Just re-enforces an area that might be the weak link. A beefy coil might be able to handle a lot of power, but it has to get there through the tinsel leads.
More tinsel leads than necessary can be bad though. Quad tinsel leads going to a 2" coil would be asinine. The extra tinsel leads would just add MMS and make the sub less efficient. Would lower FS if that's what you're after, but there are better ways to do that.
I know Fi had problems with their "FOAD" leads, but that's a different story.
Basically, there's a happy medium for each power requirement. Not enough tinsel leads, and you'll burn them up before you reach the max potential of the other parts. Overkill isn't as bad imo, but should still be avoided if you don't plan on completely saturating the coil with power