Not sure why preserving the misguided previous renovations is important to keep a record of.
Because history is not about embracing one point of view and destroying all evidence of other points of view. As I said, there is nothing that everyone is going to agree on. What one person considers misguided, others will consider justified. Historians and archivists have a responsibility to strive for objectivity. Instead of taking one side in a debate, the goal is to preserve as much knowledge as possible so that people have full information on which to base their opinions. Trying to destroy the evidence of things you don't like is totally corrupt, a crime against history. Nobody has the right to do that.
Preserving errors is not important to me.
Errors are by far the most important thing to preserve a record of. How can we learn from the mistakes of the past if our historians lie to us by pretending they never happened?
Restoring a Sphinx or a Sistine Chapel fresco to its original form is dicey because the artifacts are centuries to thousands of years old. Restoring a studio miniature to near its original condition should be somewhat easier given the item is only fifty years old and we have extensive documentation and photographic evidence attesting to its original condition.
True, it should be more feasible to come close to the original. But again, what if the only way to recreate that look fully is with aggressive restoration, adding new paints and components and materials? Isn't that what people objected to in the prior restoration, that it was too invasive and artificial? You're very big on authenticity to the original, so I would think you'd prefer preserving the original physical materials of the model, even if they show signs of aging or wear, over replacing them with modern substitutes that happen to look like the original.