You seem to be conflating also biological with purely biological. The parent was arguing against reducing depression to biology only, not claiming that biology plays no part in it. The link you provide does not prove that "medical and scientific mindset" views depression as purely biological - it just shows various ways depression affects/is affected by biology, which is not mutually exclusive with other things playing part in depression. I believe the current scientific consensus is that it is not even possible to clearly separate biological from psychological or behavioral in a complex system where psychological states affect biology and vice versa.

Your invitation to "educate yourself" seems condescending and unnecessary.

Honestly the random question of “what would happen if you just forced depressed people to pretend they’re not depressed” when my understanding is that is about the same as wondering what would happen if you had chronically ill folk try yoga. That is to say, a generic wellness strategy that shows condescending attitudes towards the severity of someone else’s disease. Someone with depression very likely attempted to exercise, eat right, etc and found that it is either impossible to perform when suffering from untreated/treatment-resistant depression or that their depression involves the inability to respond appropriately to exercise and a good diet.