There are three aspects to consider with artillery: safety, historical, and legal. Because legal implications trump the other two, modern artillery drill is a compromise between what was common (historical) and what is now practical (safety).
If something goes wrong involving artillery, it is usually catastrophic. Event organizers are very much aware of that and that is why training certification is required. Additionally, the use of established guidelines for crewing artillery is more than just a convenient how-to guide. Any investigation into an accident will look at those standards to see if they were followed. If not, the word negligence comes to mind and could influence the amount of damages awarded. If it is a national, state, or local government entity sponsoring the event, the perception of deep pockets comes into play.
The upshot is that accidents do happen, but the safeguards that are in place - welders gloves, tin foil, ear plugs, and lengthy intervals between rounds - minimize the number of accidents that occur and, if one happens, minimize the injury. They may not be historically correct, but they are an acceptable trade off.
FWIW.