Maybe. Mental issues for sure and such a suggestion makes only sense if Joran was aware of those problems himself. I still see it as an interrogation tool to get a confession. The police doesn't make such decisions IMO, a judge does. Jan could make a recommendation I guess.
I think it was just a strategy to get a confession. He was trying to sound nice and understanding.
Here's 2 bits from an interrogation of Christopher Porco about the murder of his father who was a lawyer known to the police. I think they strike a tone similar to Straten.
DETECTIVE BOWDISH: Honestly, honest to God. I knew your father for a long time. That's why I'm saying that maybe, maybe something got out of hand, all right? I'm trying -- I don't -- you know, I'm trying to say maybe I can -- I can help a little bit here. Maybe, all right? But somebody -- you've got to work with me a little bit, all right? I've got to try
DETECTIVE RINALDI: Listen, all right. I've known you for how long? For a long time, all right? I'm not going to ask you anything. We'll take a ride and let's try to straighten this out, okay? We're going to go up to -- we'll go and take a polygraph and make sure you're -- at least exonerate you.