I'm not certain if one should gain advantage on the grenades based on someone not seeing them when they have no stake in the interaction between the grenade and the floor that they are targeting. Sounds fishy. I'm pretty sure trees make the same noise when they fall even if no one is there to hear it.
Tho, i must say that in general throwing in to a square that someone is occupying should almost be with advantage as you can hit them or the square. shrug
The Doge spam movement is pretty silly anyways. Maybe dodge movement dancing could be known as "Doing the Doge"?