I am 23 years old and my doctor prescribed Minoxidil. Will my hair go back to thin after I stop? (photos)

3 weeks ago I went to a Hair Restoration Surgeon and he told me I only have thinning hair (despite having told him that both my dad and aunt have really thin hair and told me it is not genetic) and not androgenetic alopecia. He prescribed me Minoxidil 2% twice a day for 6 months. Although I told him that I was worried that if I stopped the medication after 6 months my hair would go back to being thin he told me that since I was not experiencing hair loss this would not be the case. Is this true?