Only some versions in the parent are updated when using sub-projects

[markusjevringsesame]

Hi. I have a project which has a main build.gradle, and 3 sub-projects. We use the parent project to define versions for the sub-projects. It looks something like this:

buildscript {
    ext {
        springBootVersion = '3.1.0'
        internalLibraryVersion = '1.2.3'
   }
}

In each sub-project, we reference these versions like this:

implementation "org.springframework.boot:spring-boot-starter-web:$springBootVersion"
implementation "com.internal.library:my-library:$internalLibraryVersion"

When we run the plugin, it detects that both spring boot and my-library needs to be updated. It clearly prints which version updates are needed, but ultimately only the springBootVersion line in the parent is updated. If we use the versions directly in the sub-projects, the other libraries are also correctly updated. It's clear that the update mechanism works, and that it can read the correct version from the repository etc, but it just isn't updating the versions in the parent. Any thoughts on why this might be?

It doesn't seem to be the case that it's only our internal libraries, either. Spring-boot updates, but hibernate does not. It's very weird.