Asobo writes in the SDK documentation MSFS SDK/Documentation/03-Content_Configuration/SimObjects/00-Aircraft/Flight_Model.html: “To this aim, an original normalization algorithm has been developed, that helps redistribute global aerodynamics coefficients and tables as provided by user across all surface elements so that the final forces and moments match the ones computed by FSX. Of course, this does not mean we are finally equivalent to FSX modelling, as forces are now distributed over all the aircraft geometry. It rather means that, when suming up all contributions, and thus losing geometrical distribution information, our more general model reduces to FSX historical model. This makes our model an extension of the historical model, which is in accordance with the objective of retro-compatibility. One great advantage of this is to guarantee a consistant behavior for aircraft designed with the historical model when used in the new model. This requirement is actually of the utmost importance for our client Microsoft.”
What I see in my flight model mod work is the following: Asobo did not fulfill the Microsoft requirement of “retro-compatibility” completly. The success of my flight model mods - specially the Extra 330LT mod - comes from the differences between the “new surface elements model” and the old “mathematical vector model” .
Some forum members like to tell the fairy tale “MSFS 2020 flight model is the same as FSX”. If you believe this talking, please bring facts for your opinions.