It seems Turbotax (2022) calcualtion for "medical expenses for other dependants" is incorrect or doesn't provide accuarte insturctions.

This amount should be from the dependant's tax return as if they had claimed the expense in theirs, which is their eligible expenses minus 3% of their net income.

Turbotax later asks how much of the entered amount (total of self, spouse or common-law partner,
and dependent children under 18 years of age + other dependants) belongs to the other dependants, but it enters the total amount of the other dependants in to the non-refundable tax credit calculation without deducting the 3% of the dependant's net income.