The Product Owner and Functional Team Lead are the same thing in AASF™ and their responsibilities include decomposing the epics into features and then creating user stories that are decomposed from teatures. After that has been completed, the product owner then works with the development teams to ensure they have the support needed to build the right thing.
AASF™ Team Responsibilities
Agilest® AAPO™ - Adaptive-Agile™ Product Owner