Logitech C270 serial numbers should be 12-character serial numbers. If your serial number is SN0001 I suspect that your cameras are misconfigured (at the factory), or perhaps in an extreme case you might not actually have Logitech C270 cameras but possibly knock-off clones that do not have serial numbers and always provide SN0001, similar to the XIAOMI IMILAB CMSXJ22A (I provide this as an example Webcam that provides the static serial number SN0001 since no serial number is assigned to them at the factory).
I would highly recommend taking this up with Logitech customer support.
EDIT: Ok, now we know the “SerialNumber” isn’t actually the “Serial Number” of the device, it’s the serial number of the main device descriptor for the device (because there are multiple usb interfaces from the USB device, like a video interface, audio interface, and so on, and the “parent” is the upper level device descriptor). It would be interesting to find out if Logitech changed how their USB interfaces work in newer models, and instead of giving the upper-level descriptor a unique serial number they gave the unique serial numbers to the individual interfaces and made the upper-level descriptor generic? I dunno, that sounds dumb, and a backward-compatibility nightmare for them.
-Danny