Not quite true. The command "" (much like bash's !!) runs the previous command you entered. It can also be given a prefix of a command and search the history for this command.
Even better:
Add fn term%{ $* } to your profile and you can just dbl-left-click and send the old command. And since Rio remembers your last menu item selection this becomes just dbl-left-sgl-middle-click on second execution.
Pretty neat.
Edit:
Of course this does not make it much easier if you really just want to execute the very last command.
But usually you want to either
* edit the last command, because you mistyped it, in which case you can edit the old command in place and then proceed as described above
or
* you want to execute not the last but some previous command in which case this becomes increasingly useful the older the command is
See wintext(1).