I'm very surprised you would call it that because I wouldn't describe any of those FPS things as randomness. They are calculated risks, but all of those, if I understand them correctly, are about guessing human behavior, whereas randomness as many people call it is relying on or guessing computer behavior. There can be discernible patterns in human behavior in terms of camping in a certain spot, taking a certain path to an objective, being behind a certain bit of cover, etc. There aren't any patterns (or at least no obvious ones) in sufficiently random computer behavior.

You are absolutely right. I don't really consider it to be randomness either, but for the purposes of discussing artificial randomness (X% chance to hit target, for example), I think it's a good example of how games can still have a kind of random element, but one that is much more dependent on predicting what your opponent will do, instead of hoping for a lucky dice roll.

An player who is experienced with a specific FPS game knows that at specific times opponents can be at specific spots if they take a specific path at maximum speed. They know how long it takes for a grenade to travel from their hand and land at the opponent's feet when thrown in a specific way. Now it becomes all about mind games. Opponents slowing their pace in order to avoid those grenades, you delaying your grenade to predict that potential delay, etc.

But if you take an inexperienced player who just lobs their grenades in a much more random manner, the kills they get can be considered lucky. They just know that opponents are in that general direction, let a grenade fly and hope for the best.

As another example, sometimes you are aiming at a target further away, and just as you're about to take a your shot, an opponent (or an ally) walks in front of your sights and takes the bullet instead. That's a lucky kill. It wasn't planned, there was no predicting of enemy movements, it was random. Or sometimes you mess up your grenade throw, it ends up in the wrong place, but you still get a kill. That's again random luck, and a very bad kind for the player on the losing end.

These are the kind of random events that occur constantly when playing FPS games and I'm perfectly fine with them, since they're gameplay driven, not artificially added dice rolls to make the gameplay more random.