Yes but in other images if you build the image the 3rd party feeds are present.
We don't use the traditional bitbake way (MACHINE=... bitbake openpli-enigma2-image) of building images, but have custom build scripts. I use the same scripts on my own buildserver, because I need to stay in line with the build process.
Having said that, "openpli-image.bb" contains "3rd-party-feed-configs" in it's IMAGE_INSTALL, and "3rd-party-feed-configs.bb" contains everything needed to create the feed config. So if you build "openpli-image", it should contain the feed?