@star I'm probably not the best person to opine on this, since I'm not that familiar with it, but what i see is that it has lots and lots of features which can be combined in an exploding number of ways only some combinations are supported/implemented some functionality is hinted at but not concretely described the spec falls short of creating a full contract and I've ended up having to look at tianocore frequently
efibootmgr for example only implements a very specific (even if common) kind of boot entry: one with exactly two nodes, a hard drive node followed by a file path node. see the device path protocol for the full list of node types that can appear in the path to your EFI image. keep in mind this protocol is used for all kinds of paths, not just paths to booted EFI images but also to describe the default console device for example