The only reason I can think of is so that they can use the same FS in both windows and linux -but with ntfs, they already can.
Mind you, with openzfs (https://openzfsonwindows.org/) you get windows (flakey), freebsd, netbsd and linux but -as I said; I'm not sure zfs is super reliable on windows at this point.
Mind you, I just stick with ntfs -linux can see it, windows can see it and if there's extra features btrfs provides they're not ones I am missing.
I’m a die-hard ZFS fan and heavy user since the Solaris days (and counting) but I believe the WinBtrfs project is in better (more useable) shape than the OpenZFS for Windows project.
With ntfs you have to create a separate partition though. With btrfs you could create a subvolume and just have one big partition for both linux and windows.
Mind you, with openzfs (https://openzfsonwindows.org/) you get windows (flakey), freebsd, netbsd and linux but -as I said; I'm not sure zfs is super reliable on windows at this point.
Mind you, I just stick with ntfs -linux can see it, windows can see it and if there's extra features btrfs provides they're not ones I am missing.