AWS / RDS environment variables disagree in docs

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From http://docs.ansible.com/ansible/guide_aws.html:

Authentication with the AWS-related modules is handled by either
specifying your access and secret key as ENV variables or module
arguments.

For environment variables:

export AWS_ACCESS_KEY_ID='AK123'
export AWS_SECRET_ACCESS_KEY='abc123'

From http://docs.ansible.com/ansible/rds_module.html:

aws_access_key
AWS access key. If not set then the value of the AWS_ACCESS_KEY
environment variable is used.

aws_secret_key
AWS secret key. If not set then the value of the AWS_SECRET_KEY
environment variable is used.

Should these be in agreement on the name of the environment variables?
Both the access_key and secret_key differ. It may also be useful to
indicate in /ansible/guide_aws.html that the EC2_REGION variable is
used in modules such as rds.

Also, since the underlying libraries (boto, boto3) can be configured
using their own config file, can the AWS modules that depend on those
libraries fall back to the libraries using settings from their own
config files (to avoid duplication of credentials / leakage via env
vars / etc.)?