I agree with you because the whole notion that applications do not like graphics switching is bogus because it is not switching. All graphics data from nvidia's frame buffer is DMA'ed through PCIe to the intel GPU frame buffer while using optimus. So there is not real switching.
I am R&D engineer and do a lot of simulation, FPGA PAR... etc and I can tell you that the main reason for not picking the 4800 is indeed that the High DPI version does not support optimus.
It is quite simple Dell dropped the ball because they used the eDP channel to translate to lvds to drive the 1080p panel and as such cannot drive a dp panel like the high dpi panel through the same interface (intel GPU). It has NOTHING to do with BIOS what so ever. It is a hardware issue we use the same approach in our products => use eDP to lvds convertor (NPX device) to convert to lvds to drive most of the existing lcd panels.
Hence I decided to wait and I ordered the HP Zbook15 G2 with high res screen. Apparently HP did not make the same design mistake as Dell.