Set to staff default only affects first selected barline
Create a new score based upon the the Classical orchestra.
Select the first two measures of the oboes and clarinets.
Right click the barline and choose Select all similar items in Range selection.
In the inspector, remove the check from "Span to next Staff"
Click Set as staff default
Expected The barlines on both staves no longer span to the next staff.
Actual The barlines on the Oboe (first staff) no longer span to the next staff, and only the selected barline does not span to the next staff from the Clarinet (second instrument).
There is a related bug report in #287614: Customized barline spans not always overriden when extending staff barline span.