Collecting SMS consent with Client Subscription API

I’m trying to build a client side subscription using the new Client API and wondering if its possible to collect SMS consent.

The documentation here doesn’t include any reference to SMS consent:
https://developers.klaviyo.com/en/reference/create_client_subscription

However the API documentation here says it should be included in the attributes object when posting to ‘a.klaviyo.com/api/profile-subscription-bulk-create-jobs’:
https://developers.klaviyo.com/en/docs/collect_email_and_sms_consent_via_api#subscribe-a-profile-via-api

"subscriptions":{
  "email":[
    "MARKETING"
  ],
  "sms":[
    "MARKETING"
  ]
}

But the Create Client Subscription documentation (first link) specifically doesn’t include ‘subscriptions’ as an option in the documentation, so I’m working if this has simply been overlooked or is it not possible?