I can't exactly speak for every DM, but usually most DMs have their own style that is unique to them, it is why it can be hard to be a DM and go to being a player, or be a player and swap DMs. Whether this difference is an added rule, like in your example, or maybe a modification to spells, how the game works, or maybe more races and classes, all depends on the DMs own personal choice (obviously), but all DMs are unique, even if they are not having homebrewed campaigns, and have a different way of running their game, or at least, in my experience, they certainly do.