"One final bonus is that stainless is light"
Not true. Most stainless grades have a density of 8 g/cc while mild steel comes in at 7.85 g/ cc. This stainless chain might be lighter however if they're using a heat treatable grade that could be stamped then hardened, allowing for thinner wall thicknesses, lightening the assembly.
I went to the Wipperman site to see if they publish what grade of steel the chains are made of. Not that I can tell. Sprechen sie Deutsch?