ReFS is Microsoft's version of ZFS. It's less a filesystem and more what happens when you decide to make a SQL database your filesystem. It does have value, particularly in situations where you need snapshots and indexing. Development workloads would benefit from this certainly... but it still makes little sense when you should be working out of a code repository that does all that for you.
Defender DOES go ape though if development is happening within its purview. And the only real way to fix that is to dell Defender to ignore a given folder. This is a security problem, so it seems Microsoft has decided to force development into the obscure new filesystem that is harder to access via automation tools so they can flag the entire volume to Defender to relax... the performance gains are from Defender taking a seat, not the file system. ReFS itself is a memory hog relative to NTFS unless you have an Exchange message store or bunch of SQL databases on it.
Forcing this feature to ReFS volumes means exactly what you suggested cannot happen. You cannot convert NTFS to ReFS and back again. And you cannot boot to ReFS. I see little opportunity here for malware to abuse this configuration, as you'd have to be using such a system for it to be abused. Most machines have a single drive, those will by necessity be NTFS and this feature will not be available.
In related news, Microsoft quietly removed some 8th generation Xeons from the Windows 11 compatibility list with this feature release.
https://www.xda-developers.com/microsoft-removes-intel-cpus-windows-11-support/
This sets an interesting precedent... one that Microsoft has yet to actually adhere to, and yet should! If each annual feature release drops the old stuff that isn't OK anymore, the machines that are dropped have 1 year of support left to plan replacement. This evolutionary pressure would keep Windows 11 "current", as well as the platforms they live on. It would prevent the need for a Windows 12, because that was the mistake that was made with Windows 10. Yet... I don't think that's what's happening here. I'm pretty sure MS just updated a list and forgot to copy / paste a few items.
