it's a matrix.
thats webbed
and tube shaped.
I'm guessing they are referring to the chain stay to BB.
a lot of modern builds have a cast web there, not something that is easy to do in steel (pish easy in ali though). I suspect they have designed a version that can be made in Steel where by they've linked across the stays with tubes. think crane structure.
Gusset and web aren't the same thing, a gusset is between to pieces that meet at an angle, web joins two pieces that don't meet (sort of, 2 bits that meet eventual can be webbed and gusseted).