SO my question is if it is not a proper sim why does Rene Rast practice with it? Why would Nic Hamilton and Ben Collins want their name tied to it if it wasn't a real sim?
I am a backer so I think I can clarify a bit on that.
Both Ben Collins and Nick Hamilton are hired by SMS as handling consultants since the game's early development in 2011. They are paid consultants on the handling part for pCARS, unlike other drivers like Rene Rast, Nico Bastian, Oli Webb and so on. Ben Collins in particular had been extremely harsh on the handling model in pCARS's early development, especially on the excessive grip level, buggy tire slip angle and general feedback of the tire model until SMS dumped their old brush tire model from Shift 2. Then, rewrite their new finite element based SETA tire model along with proper combustion engine simulation with turbo which I remembered that after then, I only started seeing Ben Collins posting more positive feedback. As far as I know, Ben has always been a sim skeptic where he find sims, even professional racing rigs from manufacturer to be unrealistic compared to the real thing which I think SMS did a decent job in making a sim at the end. Considering that they managed to produce a physics model that could convince a skeptic to the point he did praise some cars are somewhat close to the real thing or the current rain tires actually felt close to the real thing. Not to forget, Ben Collins is the ex-Stig from top gear so there is a huge chunk of the cars in pCARS that he actually driven before.
I deal with finite element models in my daily work which I also believe that you can never simulate something 1 to 1 to the real thing on a computer as mathematical models always have limitations or inaccuracies. Especially in an entertainment product like pCARS as the simulation parameter will be scaled back further to free up resources for graphics, netcode, AI and so on but the basic principles of the SETA model, IMO, it is actually quite decent.
The other drivers such as Rene Rast(Phoenix Racing driver in 2014, Audi LMP1 driver in 2015), Nico Bastian(Rowe Racing in ADAC), Oli Webb (Sigmatech Alpine LMP2 driver on Le Mans), they all came on the project from different contacts. Rene Rast came on pCARS via contact from Fanatec where somehow, he liked pCARS and he used it for training to familiarized with the tracks and also braking. Oli Webb came on pCARS via BAC where SMS is looking for more data to simulate their BAC Mono in pCARS. Oli liked what he saw and he stick with the project since. At the moment, I cant remember how Nico joined pCARS but I know he also stayed on.
There are also other professional drivers on pCARS WMD. Tommy Miller, Corvette factory driver who also worked with SMS in Shift 2 stayed on with WMD but I am not sure what has he been contributing to the development. Maybe he is pursuing the Corvette license for pCARS or something.