Further to our recent discussion, I checked out eight different mowers
at Payless today. All had geared reduction drives plus some form of
soft coupling between the motor and blades. The only exception was a
non-grass collecting Flymow which was direct coupled, ie cutter on
motor shaft.
The grass collecting Flymows had gearoxes (or it may have been a
toothed belt). A speed reduction device anyway.
I was getting funny looks, I couldn't dismantle them of course.
So, as I suspected, the Naturist Philosopher was right.