Cost Allocation Client Extension

Summary

Cost Allocation Client Extension

Content

Is there a Client Extension for Cost Allocation in Cloud PPM as it was there in EBS?
I do see this diagram (attached) in the Cloud PPM documentation that shows the Client Extn as a possible Basis Method.
But, I don't see that option in the application which only lists the following in the LOV to choose from:

Spread Evenly
Target Percentage and Spread Evenly
Prorate
Target Percentage and Prorate

Is there anything to enable as an Opt In feature to see this?
Or it is not available at all?

Also, is there any listing of available Client Extensions in PPM?