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?