Sure, I'm not saying its optimal, optimal will always be dedicated hardware and redundancy in every layer. But my point is that you gain very little for quite the investment by breaking out the fileserver to dedicated hardware. It's not just CPU and RAM needed, it's also SATA headers and an enclosure. Most people doing selfhosted have either one or more SBCs and if you have more than one SBC then yeah the fileserver should be dedicated. The other common thing is having an old gaming/office PC converted to server use and in that case Proxmox the whole server and run NAS as a VM makes the most sense instead of buying more hardware for that very little gain.