In the Go world, they also serve as a way to gradually shift code around. Large code bases tend to have parts which are on transition from an "old" way to a "new" way, and type aliases allows you to maintain a backwards compatible stub type for a newly changed system.

This then avoids the patch of 40k lines changed as you can gradually go to different teams and get a checkmark that the changes you made to the teams code is still going to work as expected. This is usually better coordination-wise than a 40k line patch everyone has to sign off on.