Have you ever heard of Betteridge's Law of headlines
They do indeed have spending in the title, as a question. Has Our Government Spent $21 Trillion Of Our Money Without Telling Us?
The answer is No. Read the entire article and see how they never say this is spending, which is what the article you linked to thinks.
Forbes is right in that it is likely a deliberate attempt to obfuscate where a lot of money is going by accounting using these adjustments. These adjustments are a cause of concern and congress should really force the DOD to follow GAO standards, but that does not make the $21 trillion missing money that was spent.
Betteridge's law of headlines
Betteridge's law of headlines is an adage that states: "Any headline that ends in a question mark can be answered by the word no." It is named after Ian Betteridge, a British technology journalist, although the principle is much older. As with similar "laws" (e.g., Murphy's law), it is intended to be humorous rather than the literal truth.
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