Behavior on 12.0: Executing a workflow you always need to specify both profile and package. This helps when starting a workflow as to make a conscious effort in specifying the correct parameters
Behavior in 12.1 Executing a workflow now pre-populates package and profile based on the previous execution. This is dangerous as it leads to unintended deployments when in a hurry.
Is it a bug? We expect a fix for this to be able to revert to the old functionality (always ask for package and profile).