video – Why is it not possible to change Aperture in Livewiev on a Nikon D5300 when using manual movie settings?

I’ve been using my Nikon D5300 for about 1.5 years and have recently started to use it for some video work aswell. I realized that when manual movie settings are turned on and you go to Liveview, you

  1. Cannot change the shutter speed to every value – it must be faster than the number of frames per seconds; e.g. I cannot go below 1/30th when shooting in 24 fps. This makes sense to me and isn’t a problem because I anyway use the 180 degree shutter rule (i.e. shutter speed = 1(2*fps) which is 1/50th for me).

  2. Cannot change aperture at all. This is more of a problem, but can be solved by switching liveview off, changing the aperture and the go back to Liveview. I wonder why manual movie settings prevent you from changing aperture in Liveview?

I considered posting this on Video SE but decided to ask here since 1. the D5300 ist primarily a photo camera and 2. The question is not directly about recording or editing video. If you anyway think it fits better on Video SE, please feel free to migrate the question or tell me so that I can repost it there.