This is the first time I've used msilib, but it does appear that the component is marked as 64-bit:

    >>> import msilib
    >>> msidbComponentAttributes64bit = 256
    >>> sql = ("SELECT ComponentId,Attributes FROM Component "
    ...        "WHERE Component='launcher'")
    >>> db = msilib.OpenDatabase('python-3.4.0.msi', msilib.MSIDBOPEN_READONLY)
    >>> v = db.OpenView(sql)
    >>> v.Execute(None)
    >>> r = v.Fetch()
    >>> r.GetString(1)
    '{BE22BD81-ECE5-45BD-83B8-84BA45846A2D}'
    >>> attr = r.GetInteger(2)
    >>> attr
    264
    >>> attr & msidbComponentAttributes64bit
    256

As it should be according to Tools/msi/msi.py:

http://hg.python.org/cpython/file/04f714765c13/Tools/msi/msi.py#l990

Here's the comment regarding this:

    # msidbComponentAttributes64bit = 256; this disables registry redirection
    # to allow setting the SharedDLLs key in the 64-bit portion even for a
    # 32-bit installer.
    # XXX does this still allow to install the component on a 32-bit system?
    # Pick up 32-bit binary always

For reference, the Component table:
http://msdn.microsoft.com/en-us/library/aa368007%28v=vs.85%29.aspx