IIRC, we also speculated here that this was BMs main theory that HE pushed from the beginning.
However, AM stated during one of his interviews, that he knew for a fact, LE had seen one near the house. AM is possibly the civilian who initiated the narrative. Further, he said that even when lion attack was ruled out, BM told him he still hoped it was, because otherwise someone could have her, and doing things to her.
Many of the true stories of women held in captivity, tell of daily rapes, some survive and regain mental stability, others do not. There are also stories of sadistic torture, rapes, victims undergo tremendous torment, before death.
Continuing to push the mountain lion was probably form of denial for BM.
So, IMO, mountain lion theory remains simply one of the original leads, that didn’t produce any evidence.