I understand that, but that is not how SegWit is being "sold" to Bitcoin users! What achow101 et al is saying is that SegWit is fixing his horrible malleability "problem" and will help Bitcoin scale with a defacto block size increase (via a discount in how much space SegWit signatures take up), but are leaving out the fact that LN/thunder cannot function without SegWit.
LN can function without segwit. It is just a lot more complicated and has a few more
failure scenarios. With segwit, its implementation is much simpler.
If there are failure scenarios then I don't think it will work very well, nor do I think many people will be willing to even give it a try.