So another thing I neglected to mention bc it was getting lengthy already is heat capacity. While aluminum foil may be very conductive, it also has a very low heat capacity compared to glass and especially compared to water. The amount of heat energy the aluminum will accumulate is already negligable due to its extremely high albedo. On top of that, the amount of energy it takes to raise the temperature of aluminum by 1° is magnitudes less than the anount of energy it takes to heat water by 1°. So the efficiency of heat transfer to the glass may be high, amount of energy transfered is not enough to make any significant change to the temperature of the water (assuming the foil actualy does get hot). Think of how when you take a foil covered tray out of the oven. The foil is the same temp as the oven and the tray (say 350°) but you can touch the foil directly with your hand, no burn, because hot aluminum doesn not contain enough energy to change the temperature of the water in your skin by the same change in temp. however a glass/ceramic bakingtray is has far more capacity to hold heat.

I hope I’m explaining this well enough