My 1980's Kenwood TS-430 is capable of tuning in 10Hz
steps, and the modern high-priced rigs in 1Hz steps.

I'd like to make a joke about "high-priced [band]spread", but I will
refrain.

The former resolution would require the synthesizer's crystal to be accurate
to about 1 part in 100,000, which is not out of the question.

My Yaesu FTD-1000 is in storage. I don't remember its resolution, or the
tolerance of its crystals.