Pretty much yes. The charger is designed to work with traditional bench power supplies on DC. Which are typically in the 13.8V range to mimic a typical auto battery. 12V server supplies are a little low for many chargers to achieve full power. Way too low for even higher powered chargers, why some now use 24V supplies. I confirmed that Hyperion states above 13.5V input for full power, 15V max. Table at the bottom of the first page.

IR, general numbers, hard to be exact: 2 to 3mΩ per cell is good. 1mΩ or lower per cell is awesome (likely requires some conditioning). Approaching 5mΩ and up is still useable for classes other than very competitive stock and perhaps 4x4 short course. Big caveat, IR varies by temperature, charge state, and the actual device being used to measure. Despite the caveats it's a great tool to help keep track of general pack health. Just try to be as consistent as practical with the measurement method and conditions.