I've noticed this before. Grand Prix inlays exhibit the same - slightly different designs. The older ones (nickel-silver based) tend to have finer detail, while the later stainless steel inlays have somewhat simpler with less detail. I've always guess that it was a by-product of the material and how it was inlaid.
One thing I have noticed, though, is that in the mid-70s Victorinox seems to have started experimenting with stainless steel inlays, and used the same inlay patterns as the nickel-silver versions. So there are some ss inlays that have the finer detail of the ns versions. When the transition to ss inlays happened for good in the early 1980s, the newer, simpler versions were the norm.