Ultimately, over the long term, it won't matter how many players you train. Each player has a chance of injury per session.

In the short term this 'protection by numbers' can work if you are lucky. Its a bit like Train Hard 50 times or train 100 times Normal, but in reverse, ultimately the chance will get you.

It would of course be more of a tactic if the chance of injury was per session, increased by the number of players involved, but, at least in the simplest sense, that is not the case because you wouldn't be able to get more than 1 player injured.

Its another smoke n mirrors pattern like the Hard v Normal, but I still do that.