I'm not one to regularily question other people's decisions, but there's no real logic to this that I can see - the wide-angle solutions for are generally superb and certainly a lot smaller than anything available for Sony - i.e. better suited for a general carry-around. I say this as someone who also shoots FF for various reasons - I'm not protective of here, just trying to understand something I see as contradictory.
That said, I know that there are great solutions for FE - Sony 35mm, Zeiss Loxia 35mm, Sony 28mm, Zeiss Batis 21mm ... And for E-mount in general, though I find the size/quality ratio less compelling for the APS-C bodies. That was one of the reasons I never went for the Sony A6000 - the small lenses simply aren't that good (there are other issues, but those are definitely personal ones). I would have had to choose the Sigma 30mm - a lens I like, but it is rather pedestrian, and more or less a work-alike of the ... 20mm.