It's not that they were wrong, it's that costs were too high for the new buyers of Aston Martin (i.e. Stroll).
I said it on here as well before: this project for me died when AM got in troubles and Red Bull (which are the real developers of this car, AM was just a placeholder for commercial purposes) got out of the overall AM-Red Bull partnership.
I agree with you about the 4G braking deceleration.
I am sorry, but I hardly believe that, especially if this is the supposedly "diluted" current Valkyrie that we are talking about, even more so on road legal tyres.
To give some numbers:
- The T50S - which will run Michelin slicks, will weight between 840 and 852 kg with fluids, has bespoke chassis and suspensions developed for track use and probably the most advanced ground effect aero solutions of any modern car - is said by Gordon Murray himself to pull up to 3.5 G under braking
- The Brabham BT62 - which is a full track/race car running on slicks, with a dry weight of 972 kg and with carbon-carbon brakes (such as those of F1 and LMP1 machines) - pulls 3.5 G under braking as well
So I find hard to believe those claims of 4G under braking from the supposedly current road legal version of the Valkyrie on road legal tyres (whichever they are, it should not matter in terms of grip if compared to slicks).