Ask HN: When is it safe to “disable side channel mitigations” in VMs?

Latest versions of VMware Fusion highly recommend [0] that VMs with "side channel mitigations" should have that feature disabled to improve performances. From what I understood, these vulnerabilities are mostly fixed by processor manufacturers, is it correct? Do they depend also on the hardware? So, is it "safer" to disable these mitigations on machines running newer CPUs rather than older ones?

[0]: https://kb.vmware.com/s/article/79832