I made the mistake of bringing up the subject of MLC about 3 months in; that backfired on me a couple of years later when he said "you still think I'm having a midlife crisis", when he was adamantly saying he was just moving on, he couldn't get his feelings back for me, all the rest of the familiar stuff.
Actually, very early on, before I really knew much about MLC I talked to him in all seriousness about depression, as that is something I have experienced, and I know how much it can colour everything. He went away and thought, then said no, that isn't it. Ha.
Around 4 moths in he did once ask "do you think this might all be in my head?", but that didn't go anywhere.... he was right back to "I don't know if I want you in my life".
However, sometime in the year before he left he came upstairs one day and asked if I thought he was having an MLC..... at the time I said no -- I hadn't a clue about it...
And about 18 months ago, when he was realising that he had made a major mistake with a business venture and wanted out, he asked if I thought it was a weakness to admit a mistake (I said no, quite the opposite), and then sat and said "maybe I'm just continuing my midlife crisis". By then I had thankfully learned enough not to react. I'll take that as a moment of clarity.
So he may have thought it, but if he did, he now thinks that he is out, as he is happy with his new business venture and "finally truly happy" with latest OW.
Upshot: they might get glimmers of clarity, but push those away quickly.