They don't need btc reserves in order to adopt bitcoin as official currency.
Actually, they need it. Their central bank must have bitcoin reserves so that every citizen can have bitcoin at any time they want. Banks there should have bitcoin ready to be accessed for the practicality of using bitcoin in a daily basis. Also for the purpose of bitcoin being rotated in their economy. Their government will not allow that they will not have any reserves due to the supply of bitcoin being low.