I have had doctors mention that 50/50 is an average, and often used for starting dosages for newly diagnosed. Or if someone is struggling with highs and lows, some doctors may 'blame' it on not being close to that average, instead of actually checking the details of what the individual does.
For folks eating moderate to low carb, they often have higher basal, 60/40 - 80/20 for example.
Someone in honeymoon may do only basal, or only bolus, or anything in between, depending on their pancreas.
T2s may be very different ratios, based on their insulin resistance, oral meds, and how much insulin their pancreas is providing, and the amount of carbs they eat.
The right ratio / amount of insulin you need is the combination and amounts that keep your blood sugar in range. Period.
But if your BGs are out of control, with no patterns or clues on how to improve, it's reasonable a doctor may want to start back with a 50/50, and then adjust because that's what they are familiar with when dealing with new patients.