I have a XZ2 Premium and the SD speeds are the same there. I seriously doubt that this is an "issue" that can be resolved via a software update, athough I would be very happy if that were to be the case. I'm almost certain these SD speeds are baked into the hardware Sony used. Holding out hope for a magical firmware update to fix this is, in my opinion, a false hope. Sony should be called out and berated for this design decision. To think, a flagship $1K phone with SD speeds of devices from years past. Thanks, Sony.