This is not a bug. It is the expected behavior. When you actually browse through the server, BIOS information is not visible under Hardware. When you snapshot the hardware information, it is available to check under Snapshot/Audit options. Since, it is not visible directly under the server, it is also not visible when you snapshot the information.
Try this. To the left side of your snapshot job screen, there is an Include/Exclude option. Select the small folder icon in that box and then drill down to Hardware Information > Hardware. Under Hardware, you should see BIOS. Select and add it to your list of objects to include in snapshot.
NOTE: When you use Include option to snapshot a specific part, it will snapshot only that part and leave out other parts within Hardware.
Alternatively, you can try and create a component template with the parts you want to snapshot and then snapshots on the Server Components instead of the Server Objects.