« on: Today at 06:00:10 AM »
Efficiency loss from skipping a sparge depends on how strong the beer is. Light beers use a small amount of grain, so loss of wort to grain absorption is smaller than for a strong beer.
Full volume mashes also leave nowhere for doughballs or air pockets to hide, which helps counter the lower efficiency.
I regularly skip the sparge for light beers with under 4.5% abv. Not just for time saving but also for clarity as I think the cloudiness from sparge runnings can persist into the final beer as haze or excess body.
I haven't found your first point to be true. In a high gravity brew, you will lose a lot of efficiency even with a sparge but with no sparge or a "poor" sparge where I only pour a small amount of water over the grains for 1 minute my efficiency has never dropped below about 55% even for a big beer.
Also I too regularly do no sparge for small beers simply because my efficiency is already close to 90% with small beers so there's no point in making it any "worse" by taking it to 95% or more!