I guess whatever is your source, they didn't build 64-bit one. So you can ask those who maintains that repo.

It clearly should be buildable for 64-bit.

See:

https://wiki.winehq.org/MacOS

https://dl.winehq.org/wine-builds/macosx/download.html

try `brew install wine`

https://formulae.brew.sh/formula/wine

I'm no MacPorts guru, but it looks to me like the package doesn't support building the mixed-arch version (which is a practical requirement for 64-bit Wine, although it's technically possible to build a pure 64-bit version) on newer versions of MacOS (I'm not sure what marketing version "18" corresponds to). Maybe this is related to 32-bit support being deprecated in Mojave?

    if {${build_arch} eq "x86_64" && ${os.major} < 18} {
        default_variants            +universal
    }

    if {[variant_isset universal]} {
        supported_archs         i386 x86_64
    } else {
        supported_archs         i386
    }