"Case 2: the browsing context group has an IsolationLevel of Logical": why do frames with logical cross-origin isolation despite having different agent cluster keys?

[jeremyroman]

It says:

In this situation, no frame gets access to COI-gated APIs because the browser cannot support the underlying process isolation. The frame with Document-Isolation-Policy does have DOM access to the other same-origin frame.

However, in the diagram the two b.com frames have different agent cluster keys, in which case the two should have different agent clusters and thus not have synchronous DOM access to one another, or so I would have thought.

Is this an error (should it say "does not have"?), or is there something non-obvious going on here?