I would imagine its based on how reasonable the fear is; I have a (minor) fear of heights that activates regardless of how safe an environment I'm in. If I'm standing precariously on a rooftop, or just standing idly on a well-secured ladder, the fear is the same (given the same height). In my case, I can still operate without much trouble (it remains there, but I can ignore it), but if it were debilitating, I think it certainly makes sense to refer to it as a phobia.

Not just a fear, but an unreasonable fear, that limits your ability to operate.

I think a non-phobia would be acknowledging that the danger exists, but also acknowledging its risk (according to the safety of your environment), and your fear rises accordingly (linearly?).