Let's get real $1B of silver is less than 800 tons compared to 25,000 to 30,000 tons mined silver production a year than add recycled it's barely few percentages of annual production.
If they bought $1b in one lot for sure 100% it will move the spot for few days but $50m lot there are likely few dozens of industrial suppliers/brokers who on sells to average sized refiners, jewellery wholsalers and manufacturing sectors who buy at those quantities weekly
Also a person buying $1b of silver likely have many tens of billions and it's likely a rainy day security fund and not an investment. Of course if silver double or tripples in X years it is great but likely their main "riskier" investments will likely increase 10x if no mishap occurs.
Personally I also hold few percentages of my wealth in gold for a rainy day, and add more ounces when my net wealth in other investments increases, likely I will hold all the gold when I pass and be willed away.
Some members buy and sell lot of PM, too much work for me lol but i presume these members make more wealth from trades than in spot returns and others seems to indicate that majority of non property assets are in PM and continually accumulate, all three strategies works to a degree.
Anyway I am getting off track, my point was why the silliness, lol according to Google 2700 billionaires in the world, in these day and age, a billion of PM is likely held by hundreds of people.