Troubleshooting
Sony pads on Bluetooth
Over Bluetooth, a DualSense or a DualShock 4 starts in a reduced report: its sticks, buttons and triggers, but no touchpad, motion or battery. Its full report carries those too, and once something switches it, it stays in it until it's turned off.
What switches it
Vibrating it, setting its light or, on a DualSense, a trigger effect, through WebHID or the Windows app; Switch to its full report, in the pad's Controller tab, through WebHID; and in Chrome on Windows, vibrating a DualShock 4 through the Gamepad API. Games and apps built on SDL switch it by default, so a pad may come already switched.
Why PadBench asks first
The switch reaches beyond PadBench: a game running now sees the change too, and through WebHID, the browser's own reading of the pad may stop until it's turned off. So before the first write that would switch it, PadBench asks, with what it will do, such as Switch and vibrate, and Cancel.
Afterwards
The touchpad, motion and battery are read from then on. The browser's Gamepad API may stop following the pad; Compare, in the Debug tab, shows whether it still does. PadBench never switches a pad again by itself, even one it switched on an earlier visit.
Switching it back
Only turning the pad off switches it back: hold its PS button for about ten seconds, or disconnect it in your system's Bluetooth settings, then turn it on again.