I doubt they have much Bitcoin to sell
why not have some btc. if 7 billion was found only 8.5 billion was missing.
The last I remembered was that they had no BTC deposits ...although customers paid for them.
Now that 7 billion were (coughcough) "found", they actually might have some BTC.
If so, it depends on the BTC will being returned to the creditors or sold:
...FTX is negotiating with stakeholders about options for restarting its crypto exchange...
reuters 
For a restart they would have to sell assets, but I doubt they restart.