A local oscillator of 5950 MHz gives an -inverted- IF of 1940MHz for the PC card to look at, certainly within the scope of most modern tuners and I doubt very much the LNB supplier is going to bother with cut off filters within the electronics when the mechanical dimensions of the casing already cope with standard C band frequencies.
If they can sell to more than one demographic without changes to the product then you are doing a sterling job of free promotion.
Now, if your tuner can run as high as 2250MHz plus a bit then and you can find even a sniff of transmissions out there, then they may release their next batch with a 3.7 - 4.8 GHz claim on the labelling.