I'm definitely far from an expert, but if anything, my own research on the subject has led me to https://ieeexplore.ieee.org/document/8892116 and https://arxiv.org/abs/2305.06946 (among others), and there are clearly several trade-offs that will influence the result of such a benchmark : for some, Posit would need 30% more silicon area for similar??? functionality. For others, Posit32 should be compared to Float64 in terms of performance, so a win of 35% could be expected. But whether you implement a quire or only part of it in silicon will also be seriously impacting the performance. I personally chose to investigate another use case : using 16-bit (and 8-bit) Posits for the ATmega328 found in Arduino boards to replace float32 calculations for simplified RL algorithms. So in short, very likely your mileage will vary according to your domain of interest.

Oh BTW, Mister Feldman did write an article on Posit, he didn't make an implementation.