[Libguestfs] Is zerofree or resize2fs applicable to ext4?

Hi all, Can I ask if zerofree or resize2fs could also be applicable to ext4? Guestfish help of these two commands indicates that they are applicable to ext2/3. But ext4 is not covered in the help. However, I have tested these two commands in my Fedora 12 laptop, and it seems that both commands work well with ext4. So I don't quite understand why the help of these two commands only mention ext2/3. Is it a supported feature that these two commands work with ext4? Thanks. Best Regards. --Yufang