@jimvibe I’m still learning all of this as well, but I would love to give my input and hope someone who has a better understanding will join and set things straight!
From my understanding, there’s more factors that will affect extraction than just yield and time.
So, you could have a great yield (final amount of water + coffee) but still have a very low extraction. This is because grind size (and time, and pressure, and others) also plays a factor in extraction.
Example: You’re making a Chemex. You have a very coarse grind. You run water through your grinds until you’ve reached your desired yield (final liquid coffee). But your time will be very quick (because your grinds were coarse) and thus your extraction will be very low because the water was unable to spend enough time with the grinds.
To answer your remaining question (from my understanding), it is very much possible to over-extract from increasing the yield, especially if your grind size if very small and the time your water spent with the coffee is very long. But, if you see in my example above, with big grind sizes and thus quick times, over-extraction will not occur if you simply increase yield.
It’s hard to understand how the whole thing works unless you consider everything, like dosage, grind size, recipes/ ratios, and brewing methods will also change a lot.
Also, I’ve found time to be better thought of as an indicator than an element in the brewing process. It’s not the best thing to make your coffee by, but it can help show you if you’re making coffee in a consistent manner. It’s really the last thing I’ll look at when making coffee. If everything else is good, and it tastes great, but the time is wonky, I won’t think about it too much.
I know I said a lot. Does this help at all? Definitely ready for correction as well.