Anger management is someone's inability to manage anger. Being angry is not always a sign of an inability to mange anger.

I am not downplaying his actions, he is ranting for ages that's fine. He loses his shit that's concerning. But I can only go on what OP said and can't assume more. Same for you. So you have no basis for saying that it will get bad. OP has said that he's never like that. So it doesn't seem like it's a persistent issue.

There could be a whole range of other factors effecting him, including other things at the time, that could make him angry. We can't assume to know the person. OP knows him best, it's OPs opinion that we can deduce anything but not more. So when OP says that it's not usually that he is like that, we are not in a position to challenge that.

OP also might miss things out from her account. Again we don't know those things.