For some reason, the screen recording feature does something odd with the audio and video of the file. If you screen record with audio and upload to YouTube (or even try to edit in iMovie) you will notice that there is no audio. I don’t know all the details to why this is but I find it really annoying.
A quick fix for this is to use the “Encode Media” Shortcut action and then save the new file.
This simple shortcut will grab the video from the share sheet, encode the media, and delete the original from your camera roll. Lastly, it give you the option to open the YouTube app or close the shortcut.
Again, I’m not sure why when you upload a screen recording to YouTube it won’t capture the audio but this does fix the problem.