It does seem pretty dumb looking back.
It was my group who packed in hot water. We were young and didn't have all that hi tech gear back then - just our Gortex, poly, rented boots and crampons and a ton of borrowed climbing gear from the "experienced" ones in the group - who also packed in water. We left our extra water with the guys in the shack, who were very happy to have what we had extra to spare. They looked pretty ill prepared to melt snow.
Our backs were very young then and packing in water seemed like a good idea. Pack in your water and you'll have what you need when you get to Muir. No special stove needed. No wasted time making water. No fuel needed.
Several of the group ended up with a late late start and rushed up to Muir in high winds. They were exhausted by they time they arrived and joined us, which was just before it was time to head out to the summit.
Yes, we were young dumb and strong trying to summit on a 3 day weekend.
I'm older now and able to put together the right gear and do it "right" this time. That's why I'm researching now.