Actually I posted the second one immediately after the first as I try to be a stickler when it comes to the facts. I corrected my post according to what was posted on Wikipedia and that source is questionable. I definitely question their posting of a picture that states there are now three calderas overlapping Yellowstone. I think it's all the same one. Their map of the socalled "three calderas" only outlines two calderas and the Yellowstone caldera is inclusive of the same Snake River Plain caldera. They don't show three.
I'm confused as to what you are saying. The Snake River caldera, now called the Yellowstone caldera, produced low-viscosity, minimally-explosive basalt flat-surface features at the "Craters of the Moon." Why do you expect it to be different at Yellowstone?
The link that you posted, to my surprise, even reinforces what I am saying. They describe the activity at Yellowstone as a "hydrothermal activity," with the hot spot. That certainly explains the type of hot springs you find there. They state:
"Scientists agree that a fluid has moved into the region, causing an increase in volume within the upper 15 km of the crust. Wicks et al. (2006) propose the idea that a small amount of basaltic magma (molten rock) has moved out of the main caldera (causing the ground to subside) and into the area north of the caldera (causing the ground to move upwards). They discern that the magma moved along a northward-dipping sill (sub-horizontal crack) located about 12-15 km beneath the ground surface. In the past, some scientists have preferred models where deformation at Yellowstone is caused by movement of hydrothermal fluid (hot water) or gas, rather than magma. For example, Waite et al. (2002) discussed a swarm of earthquakes that occurred in the western part of the caldera, that coincided with a change from uplift to subsidence in the caldera. They suggested the swarm was caused by movement of hydrothermal fluids (hot waters and gases) from inside the caldera to the northwest. Both types of fluids (magmatic and hydrothermal) may occasionally cause the observed deformation at Yellowstone. Scientists will continue to collect information that can help discriminate among the various possibilities."
So now we have evidence that it may not be a magma plume, nor even a magma "hot spot," but may be strictly hydrothermal. Great link: 2006.