It’s a virtual environment that requires installation of an entire Linux system. The disk and memory usage is not comparable to a native Unix OS.
Everything uses some sort of “virtual environment” these days. It’s not bloat, it’s the norm. homebrew does not use native macOS libraries except the very low level stuff. It handles its own dependencies. “Regular” macOS applications usually bundle their dependencies inside the .app folder bundle. On Linux, Flatpak installs its own dependencies. Heck, for whatever reason the Bazzite maintainers decided that installing Steam within a Arch Linux distrobox container is somehow preferable to the alternatives and Steam on Linux in turn uses “virtual environments” because the various Steam Linux Runtimes are specialized Ubuntu and Debian environments and every version of Proton is its own “virtual environment” of Windows.
I’ve bought a notebook almost exactly 10 years ago for €629 that had a 1TB hard drive and that I’ve upgraded to 16 or 24GB RAM for relatively little money (IIRC around €100). Sure, if you look at the insane prices that Apple asks for even a pathetic 8GB RAM / 256 GB SSD entry level MacBook, you surely want to avoid “bloat” but for many people in the regular x86 PC world a few “virtual environments” here and there don’t make a difference and aren’t considered bloat at all. If anything, for WSL users being able to run most unmodified Linux binaries is a benefit over relying on crappy ports of GTK to macOS and such because those ports of Linux software to macOS integrates so well…