A contract isn't a subsidy... A subsidy would be giving them dollars without any particular strings attached except perhaps to use those funds to develop the product. If the contract is to provide money in exchange for services, that's called a transaction.
I see it differently: for example the fact that the US government spends a lot of money on military can in my opinion clearly be called a subsidy for the military-industrial complex.
So then if the government buys pens and reams of paper, then it's the government subsidizing office supply stores? But it's not a subsidy if a corporation spends money on the same supplies?
My employer does business with the DoD and with private corporate entities. Both the government and the private sector spend the same money and receive the same products and services. I appreciate that you have a different perspective, but I have a hard time considering my employer "subsidized by the US government" just because the government purchases our product.
Do you have a different term you use for when the government is not simply a customer, buying what they need, but intentionally funding a company in excess of the goods and services it receives? This would be more in line with the traditional definition.
I think a company can make 100% of its revenue from the government, but that doesn't mean it is subsidized. The critical criteria is if the government is directing funds for reasons other than pure procurement, such as buying votes, stimulating jobs, ect.
It is rumored that the military (and perhaps three-letter agencies) has/have special contracts with OpenAI. This can definitely be called a subsidy.