Having the decompressor updated automatically by Windows Update is a significant step up from the current status quo of installing WinRAR or 7zip once and then

Having the decompressor updated automatically by Windows Update is a significant step up from the current status quo of installing WinRAR or 7zip once and then usually never updating it for years because it has to be done manually. Microsoft will probably have more diligence in hardening the binaries than 7zip too, which resisted enabling basic exploit mitigations like DEP and ASLR until 2018 and still doesn't enable the more advanced MSVC mitigations as far as I'm aware. There's no excuse for that in an application that's expected to handle untrusted files.