I would say that your token should be manually refreshed as mentioned in the following statement in docs:

Databricks tools and SDKs that implement the Databricks client unified authentication standard will automatically generate, refresh, and use Databricks OAuth access tokens on your behalf as needed for OAuth M2M authentication.

Databricks recommends using client unified authentication, however if you must manually generate, refresh, or use Databricks OAuth access tokens, follow the instructions in this section.

As on the connection string you are not being requested to generate the token this should means it is done on behalf.