I think a lot of coaches have a default "don't trust" for parents until they learn which ones they can trust. I'm not saying I agree with that, but having coached another sport, I understand it completely.I think much of the concern is over failure to communicate in the abnormal situations you list. What causes anxiety for parents is not being able to trust that the coach will initiate communication when something like this comes up. Then you find out at move-up time when it's too late to do anything about it.
Trust has to go both ways, and I've been reading this forum for years, and talking to parents for years, and I'd say that most parents don't allow coaches any amount of trust by default. They won't trust a coach until they've shown that they're worthy of it. I think that's human nature, but it's also harmful to the relationship, and it feeds this feeling that the coaches should communicate more than they do.
In short, until each side gives the other side some benefit of the doubt, it's going to stay like this.