If we tweak the frequency to be accurate in CW, it will be off in USB and LSB by as much as the offset of the sideband to the carrier. The frequency accuracy problem is caused by the way the R4A detects a signal. Everything is fine until the signal is brought to the product detector. The BFO in the R4A is fixed in frequency. USB and LSB offsets are achieved in the passband tuner by shifting the portion of the passband that is delivered to the product detector.
Digital dials are simply frequency counters.
They work by sampling a frequency and displaying the result. If we shift from USB to LSB using passband tuning, there is no change in any signals generated in the receiver. So there cannot be any change in what the frequency counter sees. Other than that, the digital display is a handy feature. The AADE kits are easy to assemble and easy to use.