@jeffn - I was able to successfully create a cluster using the same Azure documentation, both via the REST API and the Databricks SDK. Hopefully it helps.
from databricks.sdk import WorkspaceClient
from databricks.sdk.service.compute import CreateCluster
w = WorkspaceClient(
host="<workspace_url>",
token="<databricks_token>"
)
cluster = w.clusters.create(
cluster_name="test-cluster-api",
spark_version="14.3.x-scala2.12",
node_type_id="Standard_DS3_v2",
driver_node_type_id="Standard_DS3_v2",
num_workers=1,
autotermination_minutes=30,
)