Best practices

Once you create a request, that request will always have the same reference in Power BI. But if you delete a request, the reference will be used by a new request you create for the same dimension.

If you delete a request in your workbook, make sure that you do not have a visualization pointing to that request in Power BI, because otherwise the visualization will break.

If at all possible, do not delete requests you created in Report Builder
Make sure that if you do delete requests on Report Builder, you also delete the corresponding visualization in Power BI.
If you aren’t sure: delete requests you do not need any more, then republish and go to Power BI to see which visualizations have broken