Why can't I see the 5.7K 30fps in the camera?

Due to the fact that many contries and regions are using the different video format such as NTSC or PAL, so the first thing to do with the camera is set to appropriate video mode in order to ensure compliance in your region/ country. While the supported fps in the camera is different between the NTSC and PAL.

Fow now, the camera supports 30fps, 60fps and 120fps in NTSC mode while 25fps, 50fps and 100 fps are available in PAL video format so that the reason why you can't see the 5K 30fps in the camera.  If in this case, you need to switch option to NTSC through the app.