Yes, at 60 Hz.WAIT A MINUTE - I though this unit could only support ONE 4K monitor?
However, OP managed to squeeze out the last bit of power of the GPU by setting it to 50 Hz. Since 50 Hz is not a really common standard, which may or may not supported by your monitor, and the fact that the setting is not even available without setting custom timing as OP mentioned, MS (Intel?) decided not to advertise it and stick with what its able to output at the widely-known standardized 60 Hz.
Moreover, OP also need to use the docking station to be able to have two separate DP ports.