It was a lot of fun. For the cooling of a hot object buried deeply, the ONLY avenue of escape for heat is conduction and water circulation. Radiation and convection of the magma do not come into play. The authors attribute this to the lack of unbound water in rocks. While I can not find a reference, I would be willing to bet that groundwater flow in a hydrothermal region, cooling a batholith, would still take longer than a global flood could accomodate, because water does not travel rapidly through shale.
Shales have permeabilities of the order of a few millidarcies.
The first sentence is again model-dependent. To state this objection is easy. To produce a realistic model that cools all batholiths within a year is hard. We have a good example in Yorkshire. I'm confident that in this case, timescales need not be long.