The report initially came from the New York Times. The NYT story included this:
Several outside economists are skeptical that the Saudis will follow through, saying that such a sell-off would be difficult to execute and would end up crippling the kingdom’s economy.The economists NYT references do not appear to understand the situation correctly. They appear to view the Saudi warning as a threat but the sell-off of the assets as just a threat does not make sense. There are other reasons that a liquidation does make sense.
Saudi Arabia holds some $750 billion in US securities. To be sure, it would be difficult to liquidate over a short period such a sizable amount of securities without putting severe downward pressure on the Treasury securities market. But here is the thing, if the bill does pass and becomes law, it is entirely possible, that as NYT reports, Saudi Arabian assets "could be in danger of being frozen by American courts."
The easiest Saudi assets to freeze would be the Treasury securities.
So if the choice for Saudi Arabia is between having its assets frozen, and then possibly awarded to 9-11 victims and their families, versus liquidating at huge discount prices, liquidation looks like a very sound move from a Saudi perspective.
Note: I am not saying here that Congress shouldn't pass such a bill, I am just looking at it from the perspective of the Saudi government. If the bill becomes law, it would make no sense for the Kingdom to keep its assets in any form that could be easily frozen by US courts, especially since most of the 9-11 attackers were Saudis.