> “But persona has one critical issue — it’s fictional. Of course, we create a persona based on user research, but we make a lot of assumptions about how users will interact with a product.”

A persona is an archetype (cf. Cooper et al.: About Face) rooted in the exact same qualitative and quantitative research you can derive JTBDs from. If your “persona” is a fictional character full of assumptions, it's not a persona.

The last time I created proper personas with my team (over a period of 12 months), there was not a single assumption in there. In the end, JTBDs and personas are simply different representations of the same underlying facts/truths.