For an even extraction, you need to maintain a column of water above the coffee
I don't have to maintain a column of water above the coffee to get good extraction. No, it's not a perfect immersion, but the coffee stays saturated about 2/3 to 3/4 of the way up the column. When we've allowed the water to go above the top of the bed, the final extraction ends up more bitter.
There are far too many videos of people using drip towers improperly. Typically you will see a bed of damp grounds with an incredibly slow drip, and advice about how it can take 12 hours to brew a batch. If you do it this way, you are just dripping water down the centre of the bed of coffee and getting an incredibly uneven extraction. You're also wasting a huge amount of time, because you can easily get a proper extraction with a 60-90 minute brew time.
Our method is 210 grams of coffee, 2,700 grams of ice water resulting in about 2/3 of a gallon liquid coffee in roughly 8 or 9 hours. Out of all the brew methods we tried so far, this one tastes the best and results in a TDS of about 1.53 - it's higher and slightly more concentrated since ice will be added to the cup later.
The coffee and roast level has a significant impact on overall flavor of course, but we tried different ratios, grind, water temp, drip rates, saturation methods, etc and the above formula has worked best for most coffees. I guess the only way you could be convinced is if you tried a cup. Most people who try it really like it, including Dan.