When you start BJJ, guard passing often feels like a dangerous pass on a tightrope facing down a perilous monster far more powerful than yourself, and as the more you struggle, the more futile it all feels and you ultimately perish....
The first part deals more primarily with the stomp (made more visibly popular with Keenan's match with Miyao but also guys more recently stomping the spider-guard to break through) but Sebasian was clearly ahead of the curve here.
The second part is interesting in that it shows Sebastian leapfrogs past sidemount or knee on belly in preference for circumventing all of that/those smaller battles right to a north/south position, something, I would imagine, most guys spend far less time in. Rather than short changing himself, perhaps if you want to call it that, Sebastian goes right past those stops on the railroad and heads directly where he wants to be, north/south.
I always think of Justin Rader in moments like this, and an interview where he said "the guy who gets where he wants to be first, wins." Sebastian is doing this as he bypasses the battles for sidemount and knee on belly or from there fighting to pass back in the other direction....by just going all the way past, way past in fact.
The only breakdown perhaps I've seen is that if/when the opponent turtles, if he doesn't get the back take, the only actual points Sebastian may incur is an advantage by forcing his opponent to turtle.
This of course then becomes a matter of preference and style then: bypass the battles at sidemount/knee on belly to perhaps take a relatively direct line to the back based on the assumption that your more effective there than your opponent, or perhaps, get mired down in a lengthy battle to settle into sidemount then knee on belly.
As with all strategy, it depends on where you'd like to be as a result of the strategy and the cost/benefit analysis.
At the lighter weights and as you move up in belt level/experience, the statistical probability of points scored from a full out guard pass drops remarkably. Bishop BJJ did a great study of points breakdowns at the higher levels of competition and by weight class that support this. In fact, other tournament point breakdowns by weight class and skill levels affirm this trend.
If that is truly the case, then Sebastian's guard passing makes all the more sense. He's bypassing a position that in all likelihood is low probability to achieve and is doing so in a manner that less of his opponents will find themselves being familiar with as a guard passing strategy to defend.