permit the government to raise armies (consisting of full-time paid troops) only when needed to fight foreign adversaries.
And indeed, this was the common practice at the time. Hardly to be seen as an alternative to non existant standing armies. It is just how things were done.
The Founding generation mistrusted standing armies.
Maybe. But there was no provision for a standing army in the Articles of Confederation and no precedent for one. Standing armies weren't even a thing throughout the middle ages. Rather armies would be "called up" as needed, from the general population.This was the case in the English Civil War, and in the many American wars with native people, and indeed with the American Revolution. Hard to say people distrusted a thing that had not existed for 2000 years.
a standing army is one of the greatest mischiefs that can possibly happen