USPS is a special case of government services which is neither a traditional agency nor a government-owned corporation. Its got a weirdly specific charter that was carved out to protect private shipping companies- for example they cannot buy their own planes. They simultaneously have to deliver mail to all US addresses with uniform pricing 6 days/week AND be operate without tax dollars. I use the term loss here because that is what they use, for example in their annual report: https://about.usps.com/what/financials/annual-reports/fy2019...
https://postalnews.com/blog/2015/05/09/postal-myths-2-the-us...
I think you might have reversed your suggestion?
This was my cynical suggestions for a consistent terminology.
Even government agencies (even the military!) can't spend inordinately, they have to fit within a topline like private companies have to.
There are differences of course but there's a lot of similarity as well.
incredibly simplified
The military budget is decided by a sort of committee (many of them, in fact, and not just Congress), but private companies all have ways of parceling out a budget as well, it's not as if most staff are literally paid out of their own personal direct sales. And the way that budget is decided almost invariably involves committees. The current DoD funding model was actually taken from what Ford Motor Co. used in the 60s.
When we were at risk of government shutdown earlier in the week, our office within the agency was relatively immune to the potential shutdown as our civilian staff are nearly all paid out of 'working capital' funds which are modeled after a direct earnings model, rather than being paid out of 'appropriated' funds which would have been at risk absent action from Congress.