That's strange...
The curly braces enclose optional parts, i.e. /{,var/}run/aethercast/dhclient*.leases lrw, means /var/run/aethercast/dhclient*.leases lrw, and /run/aethercast/dhclient*.leases lrw,
The curly braces ({}) make this rule apply to the path both with and without the content enclosed by the braces.
https://www.novell.com/documentation/apparmor/apparmor201_sp10_admin/data/bx5bmkc.html
P.S.: because I'm usually on the dev channel and update rather frequently, I wrote a script to re-apply the change after each update: https://gist.github.com/Ingo-FP-Angel/905c5655511435b0ded2eb354dab538b