That is correct. As of v201402, you cannot enable enhanced CPC using the API. Once enabled from the web interface, the Keyword Performance Report should return
ENHANCED_CPC as the value of the field
BiddingStrategyType. You would, however, want to wait up to 24 hours before checking for the required value in the report. You can find more information about our data freshness policy
here.
If you still see issues after 24 hours, please provide me with the report definition and your customer id. Please click on Reply privately to author when responding.