The VMware Driver option doesn't work because it starts too late in the kernel initialization process (it's a kernel driver). Microcode updates need to be reapplied at every boot, because the CPU doesn't have non-volatile memory. It's normally the BIOS that applies it during boot so by the time the OS starts, the OS will see the new microcode. In this case, the WIndows kernel sees the old microcode before the VMware Driver kicks in and applies it. Because of this it disables its own software-based Spectre mitigation. The VMware driver can be used to test if the microcode update for your CPU contains the Spectre patch, but that's about it. It won't actually be used. The result from Microsoft's Speculation Control Validation PowerShell Script will look like this:
Hardware support for branch target injection mitigation is present: True <-- microcode contains the patch
Windows OS support for branch target injection mitigation is present: True <-- Software patch present. Windows update installed.
Windows OS support for branch target injection mitigation is enabled: False <-- Support disabled because the microcode update got applied too late

and lower:
BTIHardwarePresent : True
BTIWindowsSupportPresent : True
BTIWindowsSupportEnabled : False

PowerShell proof:

https://imgur.com/a/UB6N6