Is this something you teach now? ....from the video it just seems as Luis Ortiz circles towards the fighters power hand and very instinctively counters when they throw it almost as if he baiting them.
If you've ever watched a certain irishman's fights in the cage, the number one set up he used for his left hand was after he's slipped outside his opponents right hand.
Hits to the open side are super effective; understanding this means you can also play off of it. In a closed stance matchup, this (generally) makes your lead side powerful. In an open stance matchup, this (generally) makes your trail side powerful.
In the open stance matchup, many people tend to tunnel vision on their cross to hit the open side a lot more than they might do with their jab in a closed stance matchup. (As it happens, slipping outside an opponents left hand jab and coming back with his right or a simultaneous dip jab was a specialty of Joe Louis, in fact)
Michael Bisping made frequent effective use of his looping lead hook, a lead overhand practically, over his opponents lead shoulder vs southpaws like Anderson Silva or Luke Rockhold (which tend to be more common in MMA due to people liking to lead with their strong side for grappling exchanges).
Rockhold himself would take advantage of this principle through his love of slamming in trail leg roundhouses to the body and head. You might say it became something of a crutch even, as he had certain habits (or more specifically, an
absence of certain habits) that would not protect him ere he ran into someone savvy enough on the feet to not crumple under the (it must be acknowledged, significant) weight of Plan A.
Ryan Hall, another grappler turned impromptu southpaw striker, also made use; in his case with a lead leg hook kick to engage the open side from furthest range. A rare but effective solution that gave Gray Maynard fits all night in their meeting together.