I sent him a message, and he just replied: mm-hmm, okay. Is it perfunctory or?

Some people are like this. You send him a 70-word message, and he says, Oh, I'm so angry with you, but it doesn't make any sense. It is good to be able to communicate and understand. Maybe he is a simple man. When things are done, 50 words to reply to you are redundant. If you can't do it well, it's just empty talk to reply to you in 50 words.