Why not? It's also not like this is a foreign established manufacturer like Toyota, it's an Elon Musk joint, I can't think of many less trustworthy businessmen off the top of my head. I think they have every reason to doubt any promises Tesla makes, and doubt its future as well.

Don't accept promises, get written contracts with expensive penalty clauses.

That's a good idea, but never seems to happen; certainly it didn't in this case. Even when it does, the penalties are inevitably a fraction of the realized profits.