If you work on the web, you deliver video in 1080p. 4K is 4x the size of 1080p so you can get away with the 'cut-in'
I don't mean this as a knock against Lynda (from whom I created the gif). They make great videos and their presenters are awesome. 4K is just a wonderful newish format that allows you to cut within the same clip without an apparent 'jump cut' if you deliver for 720p/1080p.
I love it because it solves an editing problem. I hate it because it's a high tech solution to a lo-fi issue.
Did your talent mess up on camera? Don't roll another take, we'll use a 'cut-in'.