Emotionally abusive parents is what is described
How is a quieter than usual Dad an abusive parent? it is an absolute exaggeration.
Let me explain: a ranging alcoholic, violent father, would trigger all emotional alerts on a kid. As soon as said father arrives home, the kid would be on edge.
So, in a post like this, they basically skipped over the entire context of the raging alcoholism... instead they said it's a red flag when parents arrive and open the door.
I understand the context is supposed to be implied; but the post is just very poorly written. It would be like me saying "you learn quickly to protect your face from a bite as soon as a dog barks"... dogs bark all the time, very few would eat people's faces. In this example, a simple slam of a cabinet or a quieter then usual dad could mean 100000 benign things. OP should have been clear that this was already an abusive environment or at least select better examples of "alerting" behaviour