pyyaml vs ruamel behavior

script.py

#!/usr/bin/env python

from io import StringIO
import sys

import yaml
import ruamel.yaml

yaml_example = """
common: &shared_list
  - 1
  - 2
  - 3
  - 4
shared_desc: &shared_desc "A long description string shared by multiple items"
objects:
  first_object:
    description: *shared_desc
    some_list: *shared_list
  second_object:
    description: *shared_desc
    some_list: *shared_list
"""

dat_yaml = yaml.safe_load(StringIO(yaml_example))

rml = ruamel.yaml.YAML()
dat_ruamel = rml.load(StringIO(yaml_example))

yaml.dump(dat_yaml, sys.stdout)

# common: &id001
# - 1
# - 2
# - 3
# - 4
# objects:
#   first_object:
#     description: A long description string shared by multiple items
#     some_list: *id001
#   second_object:
#     description: A long description string shared by multiple items
#     some_list: *id001
# shared_desc: A long description string shared by multiple items

rml.dump(dat_ruamel, sys.stdout)

# common: &shared_list
# - 1
# - 2
# - 3
# - 4
#
#
# shared_desc: &shared_desc A long description string shared by multiple items
# objects:
#   first_object:
#     description: *shared_desc
#     some_list: *shared_list
#   second_object:
#     description: *shared_desc
#     some_list: *shared_list