I'm convinced - though i know other are not so sure, but i feel a case against Tesla could be launched for breach of contract for those people who took delivery of a car without USS that was present at the time they ordered the vehicle.
Contract law says - There has to be an offer, an acceptance - and for a consideration (money) at that point the contract is sealed.
So Tesla advertise the car with USS and state a price. You accept that offer and put a deposit down on the order. It is at this specific point the contract is made.
Those who were informed a week prior to collection that they may not have USS or will not have USS would then become the breach of the contract. I accept Tesla may inform you prior to collection of the absence of USS and you can choose to reject if you wish - but you can also insist they discharge their obligations under the contract they agreed to as the contract was formed at the point the deposit was paid - which was well before the advisory USS would be removed.
They may argue you had an opportunity to walk away, and deposit refunded, but the consumer also has a right to reject that change and even accepting the car knowing the USS has been removed would be covered by the unfair contract terms Act as a last-minute change and outside of the contract agreed.
for example - If you state an intended purpose of a product you want prior to paying - and the product couldn't possibly do what you wanted - If the retailer sold you the item knowing what you were going to do with it then it has to be fit for that purpose. So, if you bought a 1-ton pickup truck and told the dealer you were a sculptor and need to load 1.5 tonnes onto the truck - and they sold you that truck and the wheels fell off doing it - the retailer is liable and responsible - and a breach of contract.
I studied law but I'm not a lawyer, but who would go up against the world's richest man? probably only Bezos to give Elon a bloody nose.