Read the addendum closely. I will bet it probably says that a Fannie Mae lender for a new buyer will require the six months.
If you buy a property from anyone, you have the right to sell it for ten times that amount the next day. No one can control your profit. A lender can restrict a buyer from overpaying (in their eyes), however.
When I tried to get an REO under contract, it had an addendum that I could not sell for more than 20% within 6 months after closing. I flip houses in 3 months. Do all REOs, and HUD,VA for that matter, have this addendum?