compexshop is not operated by compex and sometimes they have errors in their descriptions. http://www.compex.com.sg/ is the homepage of compex.
I have not seen any and i doubt any real ones may exists.
Two single sided half-sIze miniPCIe cards plus a PCIe bridge may fit on one full-size double sided miniPCIe card. So 2 cards on one may work and count as simultaneous dual band but in the end they are 2 cards and a bridge chip.
They don’t make sense either. A multi radio single interface card would mean you lose usable bandwidth because it is one interface. A multi radio multi interface card would work like the bluetooth + wifi or umts combo cards. 2 devices in one case with 2 external interfaces (miniPCIe for WiFi and USB for bluetooth or umts) possibly routed through a bridge. This may exhaust the bandwidth on the PCIe side and limit there. This is no problem for NGFF/M.2 cards with 2 or 4 PCIe Lanes but miniPCIe has only one lane.