Some reports are accepting parameter fields some are not.
Are there any guidelines or recommendations?
The only recommendation I can make in good conscience is to “not use Crystal” anymore. The version of Crystal that we used to support is so old, there are challenges. Epicor announced many years ago that we Crystal was going away, and that we would be supporting SSRS in the future. I know that this is an extra burden when upgrading from 9 to 10, but you will be better off in the long run in making the change.