I think "I love you but I'm not in love with you" in mlcspeak may roughly translate to "I'm bored with you".
This translation would be consistant with their adolescent behavior. How many times have you heard an adolescent say, "I'm bored." The OM/OW is a person with whom they have found excitement. That newfound excitement does not last, explaining why many move from one OP to another and why relationships formed during this time rarely last.
Maybe still loving and feeling connected to their spouse is an indication of a mild case of mlc.
Sorta like: mild heart attack limited thermonuclear war small tornado etc.
"The answers are within you" (can't remember who). Unfortunately, so is the bullshit.