The product team replies that OHS 14.x is different series than OHS 12.x. Hence, certification request is needed with Product Managment to get OHS 14.x certified with 12.8 WebAgent.
i.e. this is an enhancement request, please help customer to open an idea ticket on our community,
https://community.broadcom.com/ideation/allideas?Page=1&CategoryKeys=a8f7c149-9616-4e6c-8daa-c9a4b9fe7898&StatusKeys=&Sort=MostRecent