Since the EHT is an interferometer, the observations contain less information than what would be available from a single telescope of the same equivalent size. Therefore to reconstruct the 'full image' you need to find the model which best fits your interferometric observables. As far as I can tell, what they've done with PRIMO is basically a fancy version this kind of modelling. The data isn't necessarily being guided towards the simulations, it's more like we have a better computational technique to precisely fit the data.