This is likely just an oversight in the vardeps in package.bbclass, but I wanted to open a bug so it doesn't get forgotten.
PACKAGEVARS needed PKGE, PKGR and PKGV adding.
Fixed in master: http://git.yoctoproject.org/cgit.cgi/poky/commit/?id=58977a94dd5e4d2afd6ccba84a6c67e48ab7bf16