Your definition is quite horrible. Here I asked ChatGPT in your stead to explain it better:

What is a Defense Contractor?
A defense contractor is a company that provides products or services specifically for military use, usually under contracts with the government. But who exactly counts as a defense contractor? That’s where things get tricky.
Let’s take the Humvee as an example. The company that manufactures the Humvee, AM General, has a direct contract with the U.S. military to supply these vehicles. Because of that, AM General is 100% a defense contractor—they are directly providing a military product.

Now, let’s break it down further:

What about the company that makes the glass for the Humvee’s windows?
If they specialize in military-grade armored glass and regularly supply it for vehicles like the Humvee, they would be considered a defense contractor.
But if they mostly make glass for regular cars and only a tiny fraction (say, 0.5%) of their business is military-related, they wouldn’t usually be called a defense contractor.

What about the company that makes the steel used in the Humvee’s body?
If they primarily supply the military, they might be considered a defense contractor.
But if they’re just a general steel company that sells to everyone (construction, automotive, etc.), they wouldn’t usually be labeled as one, even if some of their steel ends up in Humvees.

What about the Chinook helicopter that delivers the Humvee?
The company that builds the Chinook, Boeing, has military contracts, so they are a defense contractor.
However, if a civilian cargo company is just hired to transport the Humvee, that doesn’t make them a defense contractor—they’re just providing a service.

So Where Do We Draw the Line?
AM General (Humvee manufacturer) → Definitely a defense contractor.
A company making specialized Humvee armor or windows → Usually considered a defense contractor.
A steel company that happens to sell some steel to AM General → Not really a defense contractor.
Basically, if a company’s primary business is supplying the military, it’s a defense contractor. If it’s just selling a product that happens to be used in military vehicles, it’s not. The term "defense contractor" mainly applies to companies that actively work with the military rather than just being somewhere in the supply chain.

So basically the above explains clearly what a defense contractor is. You thus cannot include SpaceX, X or Anthropic even in this. BUT the main difference is that Anthropic openly said going forward they will be working directly with Palantir. While Musk's X (formerly Twitter) hasn't said anything like that. In fact their AI department is relatively new because it didn't exist during the Twitter times. So no, these are not the same use cases. SpaceX is a defense contractor, X is a private company, and Anthropic is a private company (former) turned into a defense contractor because it's directly working with a defense company.