In ArcGIS Desktop we used MapLogic to create Map series. An option is to simply choose Fixed Scale in the Scale/Extent properties. Now in ArcGIS Pro 2.9 the map series option for extent has Center and Maintain Scale. There are a few odd cases where based on the scale for the map (dictated by the client) the polygons for the layer on a particular map series page has polygons spanning a greater area than visible at the fixed scale. For those we would manually shift the layout to customize the view and create a Map 1 of 2, Map 2 of 2, etc to get all polygons while maintaining the scale. As these are the exception it has not been a problem to stop and work those few maps. Will there be an option that will allow Fixed Scale WITHOUT the Center being maintained? The same layer is used for several maps at different scales so adding a Scale Field would not be feasible as being the mapper I do not have the ability to change the data in the SDE database.
An additional comment is that to not have the map series maintain the center is useful when a large polygon overlaps in to the inset maps and to be able to move the view slightly allows it to be seen in it's entirety.