I don't think that actual testing bears out your premise that smooth shifting and slow acceleration are necessary for decent fuel mileage.
Where people waste fuel with manual transmissions is when they exceed efficient RPM ranges for no good reason.
In most cases, I think that a mid-throttle action (gas pedal 1/2 way down) up to around 3500 rpm is sufficient for both fuel economy and a reasonable amount of fun.
Your tachometer is your friend here. I don't pussy foot my MINI Cooper S at all, but in most city or inter-urban driving I don't hold the gas much beyond 3500---only on freeway on ramps or for passing, do I exceed this. then I often run right up to around 5500---beyond that it can get expensive and really makes no sense unless you are racing.
Having a 6 speed, sometimes I will rev smartly in 1st and 2nd, then short-shift to 4th. I'd rather have fun in 1 or 2 gears than pussy foot in all 4 or 6.
Also, I never EVER "lug" the engine (e.g. driving in 5th at 2000 rpm). In fact, I try never to drop below 2000 rpm in any gear except 1st. .