I do occasionally do the thing where I drop something even better than kibble in his bowl, or ask him to back away from the bowl while I add something tasty. And he has a ROCK solid drop it because he knows he get paid and he'll get paid handsomely. None of that was taught by pulling things away from him/out of his mouth.
This. When Indy showed occasional flashes of RG as a puppy, I can't say I never messed with his food as a result... but I wasn't taking things away to show him who was boss, either. I doubled down on teaching a "leave it" and if he seemed a bit defensive (and often even when he didn't) I asked for "leave it" then I took it and
gave it straight back with added yummies. I also tried to hand feed once in a while to build up positive association between hands and food. And I did all of this because, with my boyfriend's 5 year old running around and not always following directions perfectly, I
really wanted to make as sure as I could that the dog's response to someone reaching for his food or taking his food (should that ever unfortunately happen) would not be to freak out or bite.* I'd much rather his operative assumption be that if someone tries to take his food it's because they're about to give him even more food or something better than what he had before.
And I pretty much succeeded with this one dog at least. He hasn't shown signs of RG toward humans at all since those few small growling incidents as a puppy. In fact if he gets into something he shouldn't have, even something high value, I can ask him to give it to me and he'll actually retrieve it to my hand.
At the same time there are probably dogs for whom the take-and-give-better method might not work, and I hope I'd be judicious enough to tell the difference. Regardless RG in dogs is almost always insecurity-based and certainly shouldn't be treated as a "dominance" competition... it's like they think in their simple doggy way that if they don't get to eat this good food right now they might never get any good food ever again in their whole lives.
* The dog isn't allowed around children unsupervised at all, if you're wondering... but I'm a contingency planner.