Without properly knowing the business goal, redesigning the UI won't do much but show that you know how to do UI.
There's an episode on Netflix's Abstract: The art of design, on redesigning Instagram. That's the best example of redesigning a product, while taking into account both the business goals and your users. Doing 300 iterations of the logo to show how you got to your solution.
In the absence of a real portfolio, yes, these make sense. But they make sense if you document them properly.
Without properly knowing the business goal, redesigning the UI won't do much but show that you know how to do UI.
There's an episode on Netflix's Abstract: The art of design, on redesigning Instagram. That's the best example of redesigning a product, while taking into account both the business goals and your users. Doing 300 iterations of the logo to show how you got to your solution.
In the absence of a real portfolio, yes, these make sense. But they make sense if you document them properly.