If you use a BOM which is used by scope import which means only to take into account the dependencyManagement part. Excerpt from the docs:
This scope is only used on a dependency of type pom in the
section. It indicates that the specified POM
should be replaced with the dependencies in that POM’s
section. Since they are replaced, dependencies
with a scope of import do not actually participate in limiting the
transitivity of a dependency.
To define plugins you should use a parent where you define the plugin versions via pluginManagement.