Paul snipped-for-privacy@needed.invalid wrote
That's not what he is talking about, he's talking about wild yeast getting into the fermenter either by no sterilising the fermenter properly before using it, wild yeast getting into the fermenter by during fermenting or with traditional brewing by letting wild yeast get into the wort when before adding the brewing yeast.
Some of the barmen ask you which way you want it poured.
And plenty of home brewers use kegs, not bottles.
Normally only the filtration step when kegs are used.
Normally they don't and that's why the barman asks you how you want it poured from the bottle if they pour it.
Its actually a hybrid between homebrew and commercial beer.
Plenty of commercial beer is nothing like yellow.