why does upgrading my android application to AGP 8.4.0 make my application crash with a runtime class not found exception for greenrobot event bus?

the green robot dependency is source from another library conrolled and published by my organisation on git hub

to fix the issue i had to also add a gradle entry for greenrobot in my application e.g. api("de.greenrobot:eventbus:2.4.0")

why would i need to do this when before upgrading everything build and ran fine?

something that is “strange” is that in investigating this issue i found greenrobot was declared in our library as

implementation 'de.greenrobot:eventbus:2.4.0'

not

api 'de.greenrobot:eventbus:2.4.0'

Now i am more confused as i do not understand how it ever worked