Whenever direct to a waypoint is selected, whether that is with 'direct to' or 'intercept course', the distance calculated and displayed is always simply direct to the waypoint from present position and not direct to that part of the new leg that you're currently pointing at (it is always irrespective of the current track of the aircraft). The only difference with 'intercept leg to' is that it creates a specific LNAV course suitable for intercepting (perfect for a non-precision approach or re-intercepting the centreline of an airway).
Try it next time in the aircraft - both cases - and the distance will be the same, even though the LNAV magenta line will appear differently.