When you add the first widget in the sidebar it’s a refreshing customizer completely and not partial refreshing.
- Go to Customizer
- Go to the Widgets panel.
- Remove all the widgets one by one.
- At the last widget when you remove it, it refreshes the customizer.
- When adding the first widget it again refreshes the customizer.
- First onward, it partially refreshing the customizer as expected.
Please find the attached video for further reference: https://a.cl.ly/WnulD9r6
Is it the right behavior?