What's the point of app3 example?

[savinov]

As you mentioned in option3, it's possible to use BOM to override dependencies declared in parent project. Maven version must be 3.4.0 (which is not released for some reasons, but 3.5.x is available). The version of the artifact in the parent project wins over imported in BOM, doesn't it? Why app3 requires maven 3.4.0? I can't find any specific features about version overriding there.

For example jackson dependencies declared in spring-boot-starter-parent can't be overriden by importing BOM.