The chinese government tells that way because they afraid that the things they've serve will be useless because of the digital currency like bitcoin and altcoins. I think they suggest that because the price of it are not stable that's why they don't want to have a connection on this. But in reality cryptocoins gives us more benefits and profits than gold and silver.
The volatility in bitcoin/crypto indeed made the Chinese government anxious. this will be very disturbing and will cause panic. because of that the Chinese government recommends investing in silver and gold.