Calamares is ExclusiveArch to the architectures where live images (and GRUB, but that's a superset) are supported, i.e., the architectures listed in the "livearches" list in anaconda.spec. This is by design: It exclusively installs live images, so it does not make sense to build it anywhere else. Note that the initial packages were missing the ExclusiveArch. This resulted in a broken dependency on grub2 on ARM.
This package has changed maintainer in Fedora. Reassigning to the new maintainer of this component.