I think when people say that, they’re referencing high N urea-based lawn and garden fertilizers which can burn plants if improperly applied. Easy to overdo concentrated readily available fertilizers, hard to overdo, say, worm castings which are what, 1% N? Commercial formulations for outdoor use also tend to use cheaper forms of nutrients with higher salt indices, like urea instead of nitrate, chlorides like Potassium chloride, etc.
30% N urea based and other high-salt-index fertilizers applied without enough water in too high amounts can easily burn plants in warm dry conditions. You can do the same thing with “organics”, it’s just harder to overdo due to relative concentration and availability. Dog piss will burn grass faster than just about anything and that’s “organic”.