I can drink excellent light lager in 4 weeks grain to glass. That's 2 weeks in the fermenter and 2 conditioning in the keg.
I could get out of the fermenter a bit faster, but, I always wait 2 weeks out of Diacetyl paranoia.
I regularly tap the keg after 1 week conditioning, but, the beer peaks after another week in the keg.
I think proper water treatment, gelatin, and ramping the ferment temp along the way speed the process a lot.