Yes, it's entirely possible that Fx CFDs can only be traded, but get no prices via API. But newer Zorro versions support this with a symbol string, special types like STKCFD are not needed anymore. The symbol to get prices from GBP/USD cash, but trade the GBP/USD CFD would look like this:

GBP-CFD-SMART-USD!GBP/USD!GBP/USD