Heating up is not the issue, my bed heats up quick and is near spot on with the reading the lcd gives.......ender3 pro. It is flatness I was more concerned with. I did watch the video, even though he tended to ramble on a bit. The part I found most concerning is the heat on all beds is not evenly dispersed.......and with todays technology you would have thought that they could get the heat even all over.
The problem most people have is heating the bed initially then switching it off after a few layers are down. I leave mine on and let it cool down after print is finished. It's ok with a few small prints to switch off after pla sticks, but even those small prints curl up........very minutely.
I am in the process of building an enclosure for my ender, which will keep the heat in, as I want to upgrade the hotend and nozzle to allow other materials to be used. I am pretty sure the glass will perform well, even though it does not perform as well as aluminium.