It seems that per current travel insurance’s T&C offered as part of Premium Account, UK residents that are not permanent would not be covered for emergency medical expenses:
“you will not be covered for benefits under Section F - Emergency Medical Expenses & Assistance, or for Cancellation or Curtailment due to a medical reason, if you: … are not a permanent resident of, and registered with a General Practitioner in the country of residence”
However I would believe that quite a few Monzo customers may be long term temporary residents e.g. full time students or employees on a multi-year visas. This makes them UK tax residents and eligible for Monzo accounts, but as per terms, not for all insurance benefits. So I thought it would be rather good to have insurance that covers temporary residents in full as well.