To my knowledge... yes you are right, but this presents no obstruction to a more complete/accurate simulation of flight physics. Most flight simulators work in this way, using simplified equations that use multiple inputs to calculate one vector output for the entire aircraft. While simplified, this can produce a competitive model and can be a very convincing.
With all the preferred equations on hand from the AFM code, I don't think it would be desperately difficult to simplify/average their inputs and rewrite SFMs to be somewhat enjoyable to fly. The lack of even the most basic accepted level of flight modeling in a relaxed-realism simulator is just... depressing. Takes all the fun out of flying in Flaming Cliffs 2, which would otherwise still be a very engaging experience.
I think some additions would be prudent/necessary, mostly in the region of stability and controllability. Modeling of control surfaces and input scaling instead of assuming them would make a big difference in perceived handling qualities.
NOPENOPENOPE. :D Think of it this way... one section of the wing from the A-10 would/should count as the entire simulation of lift/induced drag for the airframe. (Two would be even better!) Very few inputs: alpha, beta (if you want to get fancy schmancy,) velocity, air density. Specific to the aircraft, just need an approximation of lifting surface area and table of values for the surface's coefficient of lift. This is no different than the current inputs the SFM uses.
I actually (with all respect to the challenges of the profession that I've only barely seen,) think it would not be that difficult to use the code written for AFMs in DCS to create simplified flight models in FC3. The primary difference would be in the format of input data, otherwise I would think the AFM simulation can just take the inputs, do the necessary math, and present the necessary output. With the rest of the environment from DCS already being used (and knowing how the part of the program related to SFMs had to be updated for FC2,) I really cannot imagine it being a big leap.
At this point, without a major overhaul to flight characteristics (and for that reason only) I wouldn't shell out for FC3.