I can see both sides of the argument but here is something from my own experience
When I was diagnosed last year I set about reducing my daily carb intake, giving up things which I loved such as chips and switching things out to healthier lower carb options, gradually reducing things down to a total of 100g of carbs a day, this was from what I learned online. My dad who is in his 80s and was diagnosed Type 2 just 3 years ago looks at how I changed my diet and admits that there is no way he could change to what I eat as he loves his roast potatoes and chips and is stuck in his ways.
Do I want my dad to get complications, No. But do I want him miserable trying to stick to an eating plan he doesn't want to and will probably feel bad about if he can't stick to it then the answer is, No. And further do I want my Mum who isn't a diabetic and eats the same meals as my father have to change to a different diet because my dad has been told he must change, No. It is why in my opinion what all this comes down to is health professionals getting to know their patients and their level of knowledge along with willingness to change rather than trying to treat everyone with the same advice.
I think that the advice should be based on what works. If the person getting the advice chooses to do something else, that is not the fault of poor advice. I'm guessing your father doesn't follow the NHS healthy plate diet either, although he most certainly would have been advised to do so.
So just because some people will choose to knowingly disregard advice that would more likely work is not a reason to only provide advice that generally doesn't work. What''s ironic is that type 2 diabetics are now all being given the same dietary advice: follow the NHS healthy plate.
People who eat lots of carbs usually can't imagine it's possible to do, but most who try are able to do it. If you are not willing to even try, there's not much hope. Of course, there's always meds and insulin for those unwilling to reduce carbs.
Why not offer 3 options?
1. Eat what your eating now, then go on meds, then insulin, then die from diabetes complications.
2. Eat to the healthy plate, then go on meds, then insulin, then die from diabetes complications.
3. Reduce carb intake and possibly avoid meds, insulin, and complications.