Yes, the Record Layer helps you define and index into _hierarchies_ of entities, but I suspect it doesn't have an answer for other access patterns (e.g. producing "report" views that relate or aggregate non-hierarchical data).
You could retroactively construct a custom view _after the fact_, but only if you can do so within 5 seconds. And (if you want continued access to that view) you'll need to ensure that that view is maintained thereafter (you would have to define your own layer -- it cannot be entrusted to application logic unless you can atomically switch to a new version of your stack). Maintaining such a view is made more difficult if your data allows updates/deletes.
The same caveat affects schema migrations. You would need to be able to fit the migration into a 5 second transaction (or tell your applications to stop modifying the data for a while, and handle it as a series of smaller transactions).
My assessment is that if you have (non-hierarchical) relational use-cases at scale, FDB really requires you to plan your access patterns from day 1. Whereas a typical RDBMS fares far better at satisfying emergent needs. That said: FDB's model is brilliant for document store and key-value use-cases.