Was told can't use minoxidil for 1 year after hair transplant? (Photo)

I had a hair transplant 2 months a go on the front of my head and middle, but not the crown and I was going to use a product called Herbal H which has 3% minoxidil just for my crown to thicken it, but my hair surgeon told me not to use minoxidil for one year, any reasons why I would like to hear other doctors opinions on this. Thanks.