In the Blueprints > Working with Components on Actors Part 1 tutorial, there are steps that say that when placing a component in an empty actor, it will replace the root component. This is old behavior. Current behavior is that the root remains and the user has to drag the component on the root if they want to replace it.
RESULT
At one point, the tutorial will talk about how placing another component in an empty actor will replace the root component, which is no longer the case.
EXPECTED
For the tutorial to match the current behavior, where the user needs to drag the component onto the root to replace it.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-47364 in the post.