I had created an SSRS (2016) Report on our reports server and this report have an email subscription which have the following report parameters:

The report is using a custom data source to our test database, then we conducted our UAT and everything works as expected, so we proceed on moving the report to the production folder within the same reports server and then the release engineer then move the report to the production folder then change the data source to a shared data source that points to production database.
Then here comes the problem, when we checked the subscription to set the parameters we were surprised that some of the parameter dropdowns got disabled.

Basically I was thinking that this should not happen because the tables and data on the Test and Production database should be identical thus the datasets for these parameters should still be able to retrieve the data even after changing the data source.
The workaround we did is we recreated the subscription (delete and create new), and now we were able to select again values for the parameter.
Now my question is, why did that happened? is this by design or a bug in the SSRS Report Server?