The synty FBX files appear jumbled when imported into blender/godot and need to be fixed before they can be used. Tested with blender 2.80 and python3.7 (but 3.X should work) on windows but should work on other OSes.

adjust_synty_fbx.py

import sys
import argparse
import pathlib
import subprocess
try:
    import bpy
except ImportError:
    bpy = None


def main_blender(raw_args):
    parser = argparse.ArgumentParser()
    parser.add_argument('fbx')
    args = parser.parse_args(raw_args)

    # In the future I want this to support processing a directory (all files from it)
    # but for now they end up with altered names so that is why this does them only one per invocation
    target = pathlib.Path(args.fbx)
    if target.is_dir():
        files = [path for path in target.iterdir() if path.suffix == '.fbx' and not path.stem.endswith('_fixed')]
    else:
        files = [target]

    for filepath in files:
        inpath = str(filepath)
        outpath = inpath.replace('.fbx', '_fixed.fbx')
        bpy.ops.wm.read_factory_settings(use_empty=True)
        bpy.ops.import_scene.fbx(filepath=inpath, use_anim=False, ignore_leaf_bones=True, force_connect_children=True, automatic_bone_orientation=True)
        bpy.ops.object.posemode_toggle()
        bpy.ops.pose.transforms_clear()
        bpy.ops.object.posemode_toggle()
        bpy.ops.export_scene.fbx(filepath=outpath, add_leaf_bones=False)


def main_nonblender(raw_args):
    parser = argparse.ArgumentParser(
        usage="python.exe adjust_fbx_for_godot.py <path-to-blender> <path-to-fbx>"
    )
    parser.add_argument('blender', help='path to your blender executable')
    parser.add_argument('file_or_directory')
    args = parser.parse_args(raw_args)
    blender = pathlib.Path(args.blender).absolute()
    target = pathlib.Path(args.file_or_directory).absolute()
    script = pathlib.Path(__file__).absolute()
    subprocess.check_call([
        str(blender), "--background", '--python', str(script), '--', str(target)
    ])


def main():

    if bpy is None:
        main_nonblender(sys.argv[1:])
    else:
        try:
            raw_args = sys.argv[sys.argv.index('--') + 1:]
        except ValueError:
            raw_args = []
        main_blender(raw_args)


if __name__ == "__main__":
    main()