@Jarhead agree.. There are scenarios where sure it makes sense.. And I can see doing it, there are pro's and cons for sure. Which need to be weighed out..
Personally I wouldn't go back to running my edge on vm ever.. The con's outweigh the pros imho.
And if you are going to run your production edge router/firewall on VM, you should have a really good handle on what that entails.
And if you do run into something where you have a question - first line of your post should be I am running this on VM, here are the details of the setup.
While in this post they do mention proxmox - they do not clearly state that pfsense is on proxmox, etc. For all we know from the first post is their proxmox could just be some other client on the network.