Think you might want to do a bit more research on LED bulbs.
With regards to OP’s post, I mean, dad isn’t 100% wrong. The bulbs will discharge their heat into the surrounding environment. However, max suggested wattage for a refrigerator is 40w so they don’t get super hot.
Was just reading through the articles I could find about it and it seems you can’t make cylindrical batteries with it. Which sucks for existing flashlights. I’m sure if the tech ever picks up some other shape of flashlight could be made.