LR LOCAL

Do you perhaps mean a CFExpress card, rather than a CF card? CFExpress is handled by Windows and MacOS as a removable external disk, not a memory card. That explains the difference that Lightroom shows.

Is it possible that the CF card that you are using doesn't contain the usual camera-generated folder structure? I just tested using an old CF card that I had used to copy exported jpegs to a Sony digital photo frame, which had none of the top-level folders that are created when formatting a card in-camera, instead it had a single user-created folder containing all the jpegs. Inserting that CF card and an SD card from my camera into a card reader, then starting Lightroom Desktop in Local mode did indeed produce the effect that you observed, i.e. CF card within the Browse panel, SD card above it (incidentally, checking the Import option in Lightroom Classic produces the same effect).

I then cancelled LrDesktop and using Finder I manually created the same top-level camera-generated folders that appear on the SD card, and moved some of the jpegs into the relevant sub-folder. Started LrD again and now the CF card appears along with the SD card above the Browse panel, and now the contents can only be copied to disk as per any other card from a camera.

I guess that's intended beahviour, i.e. if LrD (and LrC) both detect the camera-generated folders on the card, they only allow the user to copy the contents to local disk and import/access from there. But if those camera-generated folders do not exist, both Lightrooms treat the card as if it is an external drive.

So, back to the original question: does your CF card contain the usual camera-generated folder structure? If it does, then something else is going on, but if it does not then you have the explanation.