What are you guys cooking with that you think you can kill someone with mushy pasta or burnt potatoes?A lot of people are way too precious about that status of "official" content and worry way too much about "balance". PCs in 5E are so wildly overtuned compared to the monsters they're supposed to be facing that you can throw double or triple deadly encounters at even unoptimized PCs and have the PCs handily win. And as Morrus said, gamers won't die because the DM home-brewed a monster. At worst the combat goes bad and the group resets. If the players are so sensitive that they cannot handle even the possibility of losing a fight and that puts them off the game or gaming, well...not much of a loss.
Anyway, it's about creating a terrible, unfun experience because you have no idea how you are supposed to use a list of numbers. You can't hurt someone but you can sure put them off RPGs forever.
I absolutely stand by saying it is terrible advice for newcomers.