> they burn billions of dollars per day in foreign exchange

Well, given the sanctions they might as well burn these dollars/euros. So maybe it's not that bad to pump their currency rate here.

They could well unload to China, though I'm not sure if that route is still open.

My understanding was that China had restricted to some degree dollar denominated trading.

So, I think they can move their yuan freely to China still, but USD and Euros are harder to move (though not impossible?) in China

Is that a strategy to make money long term or a necessity at this point? I kind of understand stock buybacks companies do but I'm not familiar with currency buybacks.

To keep people from selling the ruble and buying dollars and euros because they fear their money will become worthless.

If Russians stop accepting rubles and use foreign currency for transactions, the Russian govt stockpile of rubles, and it's ability to print more rubles, becomes worthless. They will need foreign currency to pay people.

It's to keep the exchange rate stable. Although that can't happen if the FX reserves are frozen.