I kinda get how it works now. They force a speculative execution to do something with a protected memory address, and then measure the latency to guess the content. They did not found a way to continue execution after a page fault as rumors were.
The fact that speculative execution branch can access protected memory, but not to commit its own computation results to memory in ia32 was known since pentium 3 times.
It was dismissed as "theoretical only" vulnurability without possible practical application. Intel kept saying that for 20 years, but here it is, voila.
The ice broke in 2016 when Dmitry Ponomarev wrote about first practical exploit scenario for this well known ia32 branch prediction artifact. Since then, I believe, quite a few people were trying all and every possible instruction combination for use in timing attack until somebody finally got one that works that was shown behind closed doors.
Edit: google finally added reference to Ponomarev's paper. Here is his page with some other research on the topic http://www.cs.binghamton.edu/~dima/