I suspect that in this case the word "analog" means "similar or comparable thing" rather than "continuously variable electrical signal".
There is nothing special about the SD card reader or format on a PanelView Plus; it's ordinary FAT32 formatting in a single volume.
Because of the risk of low performance, poor physical durability, or even counterfeit devices causing problems, Rockwell will only warranty the performance and compatibility of the cards they sell.
I frequently use SanDisk cards from reputable retail outlets and have been successful with them.