In their repo, under "Limine's Design Philosophy" -> "Why not support filesystem X or feature Y? (eg: LUKS, LVM)":

The idea with Limine is to remove the responsibility of parsing filesystems and formats, aside from the bare minimum necessities (eg: FAT*, ISO9660), from the bootloader itself. It is a needless duplication of efforts to have bootloaders support all possible filesystems and formats, and it leads to massive, bloated bootloaders as a result (eg: GRUB2). What is needed is to simply make sure the bootloader is capable of reading its own files, configuration, and be able to load kernel/module files from disk. The kernel should be responsible for parsing everything else as it sees fit.