Also might add here that this site
https://morewinemaking.com/category/glass-plastic-carboys.html
has glass carboys with spigots about 1-2" up from the bottom. (This so annoys me in standard drink dispensers -- you can never get the last bit of punch out!) Not as nifty as a conical carboy but...
That's my understanding about drilling glass or even ceremic tile -- I had to buy a (get this...) *hand cranked* drill press. Electric drills are too fast and even with water coolant generate too much heat. Hence explosion, is my guess.