Why do you explicitly not recommend 7055-C for use with USB oscilloscope

Note: this is only valid for USB 3.0 oscilloscopes and does not affect to USB 2.0 devices.

The isolation method used in this model (capacitive) has a minimal but existing error rate. This is well below the required error rate according to the USB specification. However, the Picoscope firmware does not allow transmission errors at all because it is unable to perform the required re-transmission.
We therefore recommend 7055-D and in some cases 7055-E. There, the isolation method for USB 3.0 is optical and there will be no transmission errors at all.