I the confusion comes from how ADF is storing active or inactive state and how deployments use the publish branch.

When you make an activity inactive ADF writes the isDisabled as true into the pipeline JSON so when you reactivate it again ADF doesn't change the value to false but simply removes that property and that means your PR may show a line deleted as a difference and it can be easy to miss or it can't be a visible change if you edit in live instead of git mode.

So if you merged from staging to preprod and it didn't regenerate the oreorid env adf_publish the change may not reach pre prod.

In ADF, you should be in git mode where you are in staging before you save and publish and in the PR from staging to preprod shows the removal isDisabled in the activity JSON.After merging, switch to preprod branch sync and then publish again to regenerate preprod adf_publish.