From what I can see, both points of view are legal, no one is right, no one is wrong.
This whole issue from ATC and flight crew comes back to situational awareness.
When to divert, and what factors you take into account is situational awareness.
When it comes to situational awareness, there is no right or wrong answer, however environmental inputs (eg TTF, ATC, FMS, FMGC), and experience (aircraft, flying history, local knowledge) do play a big part in developing the mental model each of us use.
If TAC ON uses a different mental model, he is not incorrect, nor are others, how we weight variables is up to the individual.
What we read, every instructor, supervisor, and contemporary who has ever spoken to us has an opportunity to influence our judgment.
What is clear, is the mental model ATC and flight crew have now of the situation is not the same as at the time it developed, the reason being, we have effectively communicated information to build a different model.
