When a state simply holds it, it doesn't help the economy. However, if the state trades, the profits can generate new revenue for the state. While many people claim El Salvador is constantly accumulating, they never sell it. This situation is certainly not conducive to economic growth. Money isn't flowing directly into the economy; it simply stagnates and can't be used to improve welfare. When Bitcoin is simply held, it becomes a commodity with limited recognition, unlike gold.
Are you suggesting that instead of holding bitcoin, countries should participate in bitcoin trading in the market? That would be an even worse idea because what guarantee is there that they can make a profit from the trade? Using the national budget to trade for the purpose of making profit is no different than gambling.
When bitcoin is held or added to national reserves, it is just like gold. Holding gold does little to boost the economy either. Because the task of national reserves is to prevent financial risks and stabilize the economy in times of instability due to crises, wars and pandemics. They do not promote the flow of money into the economy nor can they improve the economy simply by holding them.