Upshifting, it isn't usually necessary, though I'm not a street racer, so I can't comment on the validity of that particular quote [0].
Downshifting, particularly into first as you're coming to a stop sign, it'll save a fair amount of wear on the synchros. Or if you have a car with worn synchros, it'll help ensure a quicker, smoother downshift in general. A 5-3 downshift on an offramp usually benefits, for instance.
[0] Given the substantial liberties they took in general, your skepticism might be justified.
Downshifting, particularly into first as you're coming to a stop sign, it'll save a fair amount of wear on the synchros. Or if you have a car with worn synchros, it'll help ensure a quicker, smoother downshift in general. A 5-3 downshift on an offramp usually benefits, for instance.
[0] Given the substantial liberties they took in general, your skepticism might be justified.