"The app-arch category contains tools for archiving, compressing and uncompressing files or groups of files." "The app-backup category contains tools for performing backups of data, including both full and incremental backups, as well as backups to other media (CD-R, Tape, etc.)." mt sends only commands to the tape drive like eject, rewind..., but does not compress files itself.
So you don't have a clue what archiving means.
Jeroen, I agree with you that "app-arch" and "app-backup" are not the ideal category names. But mt does not archive, or compress it is rather a tool for hardware commands like tape eject... All other packages in app-arch are compressing them self like zip. In my oppinion it would rather fit to app-backup (only because it has "tape" in the description) and perhaps even better to sys-block. The packages in sys-block are very similar to mt. Please have a second look at it.
(In reply to Jonas Stein from comment #2) > All other packages in app-arch are compressing them self like zip. You're wrong about that, too.