From the circumplex, I interpret what Eoghan Gardiner is describing to be near the bottom of the "Deactivation" axis. With such a low amount of "excitement", it would be very difficult to distinguish pleasure or pain even though the feeling is still there. Additionally from the circumplex, the feeling would not be very strong. But it would still be there as either a pleasure or a pain.
This aligns with my intuition. But it's difficult to intuit the idea that the absence of pain is the greatest pleasure. It’s logically correct, but when I really dig into it, it's hard to wrap my head around. At first it makes sense at the macro level, but Eoghan Gardiner 's anecdote is at the macro level. After a while it makes my head spin!
Of course, what Cicero loved to do was to find rabbit holes and dig away....