I think we're on the same page, but talking about different people/parts of the organization. In training small groups of new guys coming to the team, if they were totally fucking up we did pause or completely stop scenarios, while explaining what they were doing that was about to get them killed. We were also working with experienced officers who had applied to go to a different unit, not new recruits. Although they had been recommended and evaluated prior to training, if they couldn't get their shit together, we didn't have to hope they'd quit because that decision could be made for them.
GJM said "If your team gets killed on every entry, it quickly becomes a negative, and pretty soon your team doesn’t want to clear a house", and that's what I'm referring to. Nowhere in this am I saying that every scenario should be designed to kill every person or team that attempts it.