You know there is very little difference in concept between the concept you just outlined of governmental accounting and the accounts kept by large corporations with wholly-owned subsidiaries, partnerships and joint ventures. Each of the sub-entities can keep its own set of books and the parent corp shows a consolidated balance sheet, statement of retained earnings and statement of profit and loss for the end of each accounting period. In both the individual books of the sub-units (subsidiaries or government departments) as well as on the consolidated books of the parent company or federal government, the GAAP will still be expected to operate. Specifically, if there are long-term liabilities in either the consolidated balance sheet or the subsidiary/gov't department balance sheet, you should be able to find the long-term liabilities whether or not they have a fixed maturity date.
The web-site is conning you and you just swallow it all down like mother's milk. First of all, as I just explained, a private business is accounted for as a single entity but its single-entity balance sheet is effectively a summary of operations of its subsidiaries, partnerships, joint ventures, etc. A good financial statment will be well enough organized so that you will know how and in what amounts the subsidiary operations contributed to the figures on the consolidated balance sheet. If all that ISN'T clear from the private company's financial statements (as, for example, it was not clear on Enron's statements) then they are fucking with you.
Furthermore, since all the tax-paying citizens of the U.S.A. contribute their taxes to a single recipient, Uncle Sam, then Uncle Sam should not be hiding his fiscal managment (more likely mis-management) of the national assets through multiple accountings from his many departments without a consolidated financial statement indexed to the subsidiary financial statements so that the average taxpayer can read the story of his or her tax dollars in action. That this does not happen in real life is NOT because "it isn't done that way" or "it can't be done that way," it is because you are being fucked and you (not YOU personally, but the dumb-schmuck American taxpayer) is being bilked mercilessly by the crooks that they elect to represent themselves. There is absolutely no good reason why any government should have to keep two sets of books. Previously, keeping two sets of books was the exclusive practice of criminals and tax evaders.