I just don't understand though, what about over extraction?

Two things tend to limit the possibility of over-extracting in cupping-style brews. First, as the grinds become saturated with water they sink to the bottom of the brewing vessel and pile up; if the water isn't stirred too much this slows any further extraction significantly. Second, the falling temperature of the brewing slurry also slows the rate of extraction, especially of the tannic components of coffee. The result should be a brew that highlights sweetness and acidity, with a moderate amount of body.

Folks who like to brew this way should keep an eye out for the soon-to-be-released Rattleware "cupping brewer," which lets you brew a cupping-style extraction and then put a plunger over the grounds so that you can pour out the brew without getting grinds in your cup. Conversely, this style probably works worst in an Espro or similar double-walled press-pot, given that such vessels will hold in heat for longer.

I often use a Clever at work, and more often than not I have extended brew times simply because I get sidetracked with something and then remember to come back to it ten minutes later. I always enjoy these longer-steeped brews and I long ago bought into George Howell's advice to drink coffee at cooler temps, so I like it at the resulting lower temp anyway.

Pilot coffee in Toronto put out two interesting blogs earlier this year that help to explain why extended contact times do not overextract and how sweetness is being maximized by this method.

"Sucrose levels continue to increase up to at 14 minutes at least"

https://www.pilotcoffeeroasters.com/blo ... -immersion
https://www.pilotcoffeeroasters.com/blo ... ion-part-2

Thanks for posting these, mfogliet. Worthwhile reading.