How on earth could it be harmful? Sounds like they want you to eat more carbs now than at diagnosis.
They will probably quote lack of fibre as a reason for eating those carbs. But veggies, nuts and seeds have plenty and fibre doesn’t count towards any carb count anyway. The other argument is the brain needing 130g a day. But that is glucose not carbs needed. And glucose can be made from fat and protein if you were to actually eat zero carbs, and very few at all manage that. You’ll eat or make enough for your brain. Carbs are not essential for life. Protein and fat is.
Another argument is these lower GI carb slow or even out your blood glucose rises. They kept question here is compared to what? Yes it’ll be lower than simple nutritionally devoid sugars for example. But whole grain bread contains the same sort of carbs as white bread. And those carbs don’t disappear. They still turn to glucose and raise levels, even if by a bit less but for longer. The area under the curve remains the same. Better still not to raise it in the first place, assuming you still meet nutritional needs.