Hi Jer, I think they believe they want us to date others as a way of letting themselves off the hook, as you surmised. The reality is that if it happens or is even likely they can be very jealous and possessive. It is OK for them but not necessarily OK for us!
And yes, they are all over the place emotionally at this stage. Emotions racing around in their head as if they are on some sort of strange drug. Mood swings, anger, even occasional bouts of remorse, and loads of self pity.
As you know, most people who got through MLC have had a deeply traumatised childhood or adolescence, never dealt with. For a period of time they hold it together, often many years, while dealing with an internal despair that they cannot voice because it is so shaming to them (shaming is the only word I can think of but it isn't exactly right).
When they externalise it, they run away from their old life, including us. In their heads we are the problem, not them. It usually takes a long time for them to sort out their deep underlying problems, and some never do. All we can do is roll with the punches, and accept that these are damaged people, acting out (easier said than done).
We can use our pain to grow and become strong. Whatever happens with them (and we do not have to stop loving these beautiful damaged people) we have it in ourselves to learn and grow through our own pain. Not a barrel of laughs, but we are where we are.
Some MLCers appear to work through it fast, but these are the exceptions. For most it is a long journey.