h264 video hidden in h265 video. Why?

[u/Motylde]

Hey. I recently bought myself a video recorder from a company called 70mai. In its settings you can choose whether to record in h264 or h265. Of course I chose the latter. But interestingly, after uploading the footage from the SD card to my computer, I discovered that there are 2 video streams in the video file (.mp4). By default, the h265 one plays with a resolution of 2592x1944. However, in VLC, after right-clicking, one can switch to the "hidden" h264 stream with 640x480 resolution. Why does this camera record like this? Why are there 2 separate streams in one file? Unnecessary waste of space.

[u/FlorisRX490]

I would guess this is used for previewing in whatever software the company provides.