I know it is still generated, but from the 2.1 branch, which is no longer an active branch.
For OpenPLi 4 we introduced a branding system, to make it easier for all the "Based on OpenPLi" images out there to include their own branding without having to fiddle in the repository, and also to make sure that people cloning the repository will not produce an image that boots as an official OpenPLi image, but as a "Based on OpenPLi" image. This to avoid people coming here for support because they think they have an OpenPLi image, but they haven't,
Earlier versions don't have that system, so it would require a different solution that would mean making our bootlogo available again. Which we no longer want to do.