@gringley your recollection is spot on. The Apple hypervisor framework that Fusion uses implements Nested virtualization using an Intel chip feature called VMCS Shadowing. If the chip does not have this feature, a software implementation in Fusion is used to work around the lack of the hardware feature. That will allow nested virtualization to work on chips that don’t have VMCS shadowing but enacts a performance penalty. 

@tmaurizio if you look in the vmware.log file contained in the virtual machine’s bundle, you can easily find the Intel chip in use on your Mac. Use that to see if the model is listed in Intel’s list of vPro CPUs found here: https://www.intel.com/content/www/us/en/products/details/processors/vpro/products.html

VPro processors are the ones that have the VMCS Shadowing feature. If the chip in your Mac isn’t on the Intel list of vPro processors, it doesn’t have the feature.