"Cores on Bulldozer are only about half as strong as Intel cores. With Bulldozer, it would be difficult to run at high framerate required for VR, and not enough power for physics like on i5s. Zen, on the other hand, should be ~4 times the power than same clocked Bulldozer. "
But compare this to what the dev said---they said they were unable to get the game to run smoothly on an i5 versus an i7. So, what this tells us is that having 4 physical and some number of virtual cores is required to run this game smoothly with the advanced physics (only difference between most i7s and equivalent i5s is the virtual extra 4 cores). This indicates that unlike most games, this particular engine is very, very well multithreaded, and the Core series advantage over competing FX-series chip has always been that games are usually less than optimized for more than 4 cores.
If we look at apps that take advantage of all 8 cores, suddenly the FX Bulldozers and Steamrollers dont look bad at all. For example: a benchmark like Cinebench R15 would give me roughly 730 on my 9590 at stock settings, compared to barely 700 for my old 3770K Ivy Bridge I also benched at the time. Likewise, running Geekbench 3 on my 9590 and current 4790K---the 9590 actually manages to put out a higher score for integer than the 4790K.
It doesnt translate well to real world performance, because this is a benchmark that nearly fully saturates all 8 cores, which almost never happens in games. My point in all this is that we have a game here which is apparently a rarity---a game that can be significantly impacted by having 4 extra addressable cores (whether virtual or physical), whereas most games I've come across favor 4 strong cores over a setup that has 8 physical cores that is roughly equivalent.