Add an option (Boolean-checkbox) to have "Round scale to nearest" value for map series Map Extent: Best Fit Extent round the scale denominator up only, not up or down.
Per a detailed description with illustrations at:
https://community.esri.com/t5/arcgis-pro-questions/map-series-best-fit-extent-round-scale-issue/m-p/1269603
The Map Series definition in Layout Properties allows the map extent to be set to a best fit extent, where scale will be adjusted to show the data for each series page. This includes the ability to specify a "Round scale to nearest" number, which causes the scale denominator to be rounded. Currently, rounding will round to the nearest value, either up or down. This can cause the extent to be set so not all data are drawn.