Can't set timeout on loadbalancer listener

Issue

• We've got a loadbalancer:

$ openstack loadbalancer listener show 5ceff717-06ac-4733-ba21-02e416544b0c                                                                                                                                                                  
+-----------------------------+--------------------------------------+
| Field                       | Value                                |
+-----------------------------+--------------------------------------+
| admin_state_up              | True                                 |
| connection_limit            | 5                                    |
| created_at                  | 2020-11-23T16:40:21                  |
| default_pool_id             | 2bfe0e82-ca31-49bc-b287-e7d74b35f2a2 |
| default_tls_container_ref   | None                                 |
| description                 |                                      |
| id                          | 5ceff717-06ac-4733-ba21-02e416544b0c |
| insert_headers              | None                                 |
| l7policies                  |                                      |
| loadbalancers               | 2f9b48fe-51ba-4dbb-94df-bd4087422444 |
| name                        | listener1                            |
| operating_status            | ONLINE                               |
| project_id                  | 613fb1a21e2e46bebf8db98330cc5e90     |
| protocol                    | HTTP                                 |
| protocol_port               | 80                                   |
| provisioning_status         | ACTIVE                               |
| sni_container_refs          | []                                   |
| timeout_client_data         |                                      |
| timeout_member_connect      |                                      |
| timeout_member_data         |                                      |
| timeout_tcp_inspect         |                                      |
| updated_at                  | 2020-11-30T12:10:31                  |
| client_ca_tls_container_ref |                                      |
| client_authentication       |                                      |
| client_crl_container_ref    |                                      |
| allowed_cidrs               |                                      |
| tls_ciphers                 |                                      |
+-----------------------------+--------------------------------------+

but we can't adjust timeout_client_data or timeout_member_data:

$ openstack loadbalancer listener set --timeout-client-data 60000 --timeout-member-data 60000 5ceff717-06ac-4733-ba21-02e416544b0c
Unknown attributes for argument listener_.listener: timeout_member_data, timeout_client_data (HTTP 400) (Request-ID: req-ebfd93ca-a232-4f5b-980d-048a11befa31)

• These flags are documented in the --help for the command:

$ openstack loadbalancer listener set --help
usage: openstack loadbalancer listener set [-h] [--name <name>]
                                           [--description <description>]
                                           [--connection-limit <limit>]
                                           [--default-pool <pool>]
                                           [--default-tls-container-ref <container-ref>]
                                           [--sni-container-refs [<container-ref> [<container-ref> ...]]]
                                           [--insert-headers <header=value>]
                                           [--timeout-client-data <timeout>]
                                           [--timeout-member-connect <timeout>]
                                           [--timeout-member-data <timeout>]
                                           [--timeout-tcp-inspect <timeout>]
                                           [--enable | --disable]
                                           [--client-ca-tls-container-ref <container_ref>]
                                           [--client-authentication {NONE,OPTIONAL,MANDATORY}]
                                           [--client-crl-container-ref <client_crl_container_ref>]
                                           [--allowed-cidr [<allowed_cidr>]]
                                           [--wait]
                                           [--tls-ciphers <tls_ciphers>]
                                           <listener>
[...]
  --timeout-client-data <timeout>
                        Frontend client inactivity timeout in milliseconds.
                        Default: 50000.
[...]
  --timeout-member-data <timeout>
                        Backend member inactivity timeout in milliseconds.
                        Default: 50000.