In ArcGIS Pro, when the optional Rotation is set to None, the spatial map series keeps the value from the specific page.

Workaround

If the Rotation needs to be set to zero (none): In the layout view, open the map frame properties and click Display Options. In Location Settings, manually set Rotation to 0° after changing the Rotation value to <None> as follows: Click the Insert tab. In the Map Frames group, click the Map Series drop-down menu and select Spatial. In the Layout Properties dialog box, click the Map Series tab and expand the Optional Fields node and adjust the Rotation parameter.

Steps to Reproduce