I'm very much aware of Gentoo...but if you're going to compare basically any distribution is "poor man's Gentoo" because it's a collection of packages built from source files.
The main advantage of Gentoo is not building from source. One could argue that's the main disadvantage of Gentoo.
An ordinary Linux can be configured by installing pre-compiled packages. The system either has the package or not. Gentoo allows the package itself to be configured. Think of package ./configure arguments; they're abstracted as "USE flags" in Gentoo and allow tweaking the package internal configuration. It also allows modifying the environment variables used during the build. Setting CFLAGS/CXXFLAGS allows optimizing for the system's CPU instead of doing a generic x86-64 build.
You are rebuilding Alpine packages on top of LFS while using glibc. So I guess you want a minimal system with OpenRC.
Gentoo will give you that with proper package management including on the system part without having to do the weird dance you are making with abuild with a nicer experience if you want to patch and update your packages later and significantly better tracking on what you have done.
I have a hard time seeing anything starting from LFS which wouldn’t be better actually starting from Gentoo.
