Zeiss Batis desing on the left – Tamron lens design patent on the right
I found a newly published Tamron patent describing a Full Frame 18mm f/2.8 lens design. And as you can see from the comparison I made above it really looks like Zeiss licensed that design for their Batis 18mm FE lens. This is one more evidence of a tight Tamron-Zeiss collaboration on the development of their Batis lens range.
Zeiss Batis 18mm f/2.8 at [shopcountry 47045].