As is said in the PoC, it does not bypass index masking and site-isolation. They read data already available to the code they are executing. They did show that

As is said in the PoC, it does not bypass index masking and site-isolation. They read data already available to the code they are executing. They did show that the timer resolution mitigation is not 100% effective, which is well known and why it is not the only mitigation. That's not a speculative execution browser 0day, as it doesn't work in updated browsers and it never has (or I guess it works if you want to leak data you could just console.log). Could you post an actual 0day instead?