https://www.haskell.org/ghc/download_ghc_7_10_3#sources reads

Source Distribution
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The source tarballs provide everything necessary to build the compiler, interactive system, and a minimal set of libraries. For more information on building, see the building guide.

    ghc-7.10.3b-windows-extra-src.tar.bz2 (92 MB)
    ghc-7.10.3b-windows-extra-src.tar.xz (91 MB)

Shouldn't the two files be as follows?
    ghc-7.10.3b-src.tar.bz2
    ghc-7.10.3b-src.tar.xz