For the Sony A7R / A7 (Sony E mount), Samyang has essentially added a built-in extension tube to the rear of each DSLR lens. It’s like adding a lens adapter, but without the adapter and additional flange between lens and adapter. A cool idea for which Samyang deserves credit. It doesn’t optimize the lens for A7R/A7 mirrorless use, but DSLR designs should generally perform well due to a long backfocal distance (digital friendly).
Versatility or convenience?
With a DSLR version of the lens, it can be used on that DSLR and the Sony with an adapter (versatility), or if it’s native Sony E-mount, no adapter is needed (convenience).