This case study has been the highest signal, under 20 minute question I can ask potential PMs.
I always ask that question in that exact same way. “Tell me how you would improve it.”
The candidates I fall in love with immediately narrow down to two sets of users and go through trade offs.
They then say “this is how I can most quickly test if I’ve picked the right user.” And describe how they would measure the answer to that question and set out the next two or three steps they would take.