The consistent “need” for a stable slurry temp is just not relevant any longer. Tetsu Kasuya(Japan) just won the world brewers cup with an approach that will not ever, have a stable slurry temp much less 201F.
I tried his 40/60 method for the V60 02 and, really works! V60, the most tempermental dripper of all and this method tames it.
Coffee brewing creates “summarization” rules, to avoid considering the many, many compounds that extract at different levels to make a flavorful coffee.
As an example, maybe components at the start of the brew need to extract at 205C, midway at 200C, and at the end 195C. Or maybe agitation at the beginning, and zero at the end?
Not all components in coffee should be extracted, they are “negatives” for flavor. How can varying all these elements of temp, grind, water avoid this compounds?
Given the large number of compounds, the approximations of using a single temp, consistent level of agitation, etc., are just ways that humans try to manage all of the variables in a realistic technical way.
But in reality for brewing coffee, I could see different grind sizes layered in a dripper, agitation and temperature varied during the brewing, plus combining immersion and pour through at differing stages. All to manage the many compounds in coffee and only extract what is “best”.
What would help, though I haven’t done it yet is during the brewing, segment each pour into a different cup. Then you can taste the stage of what each pour provides to the coffee cup. Actually, you could just take each element and manually mix it together to get the flavor profile for that cup of coffee and then reverse back to your brew to replicate.
Or could take the same coffee bean and create an amalgamated version with multiple drippers extracting timing segments from each dripper and then recombining.
The possibilities are endless…
If one has the time…
So, what temp of water do you use? Can depend on many, many factors and how experimental you want to be. Medium Roast higher, Dark Roast lower otherwise… mileage will vary.