Or motorsports, like in Formula 1 where they used to designate half points if a certain % of the race had been completed but not a different % of race distance which would enable them to treat it as a completed race.
I'd say it's very difficult to achieve something along those lines and give something fair, but precedents have been set in individual stages which have wound up proving potentially decisive - and incredibly divisive at the time, but by and large become footnotes in retrospect. Take, for example, the Richie Porte motorbike crash in the 2015 Tour. Strictly speaking by the rules Froome running up the mountain without his bike should be a DQ, which would have opened up even more arguments than there already were about the fairness of the rules; annulling the stage at the time of the crash may have awarded a time bonus to those in the incident which was far from ideal, but it was better than either DQing the yellow jersey for an incident that was out of his control, or abandoning one of the most basic tenets of the sport which is protected by that rule, that being that the winner of a bike race has to race on a bike (realistically, that rule would not have been designed with an incident like that in mind, but had it been breached, it sets a dangerous precedent for future incidents, as we have seen from the way time limits are increasingly ignored by the bunch once there's enough of them not to be afraid of being ejected from the race, as seen to its ultimate extent in the 2016 Vuelta).
Less contentiously, you also have last year's Tour-deciding stage with the annulling of the stage on the descent of the Iseran and the decision to take the time at the top of the Iseran as final. Of course, had the other riders known at the time Bernal made his attack that the summit of the Iseran was the finish and they didn't need to conserve energy for a final climb to Tignes, then perhaps he would not have been given the kind of rope he was. Certainly a lot of other riders will have set their strategy out around expecting Bernal to tire riding Tignes and making tactical decisions about towing Thomas all the way to the final climb. And this is rather eased by the fact that Alaphilippe being dropped meant that the group did ride a high tempo to put pressure onto him as well. But in the wake of it, it was a very difficult pill to swallow, after one of the best Tours in years, that it would end in a kind of damp squib way with time taken at a point where nobody was really actively fighting for position and the stage - ultimately settling the GC - being taken by somebody who had been allowed more time than they would ever be granted willingly on a final climb. Yet here we are 12 months down the line, and nobody really bothers too much about it. Maybe if Bernal becomes a divisive figure a few years down the line it will be revisited and argued ad nauseaum like Chaingate or the Stelvio neutralisation that the maglia rosa decided was carte blanche to stop for a coffee, but even then, we don't really discuss the Ventoux motorbike incident much these days and just sort of accept that Froome won the 2015 Tour, and Froome is about as divisive a figure as the sport has seen since Armstrong.
However, the unifying factor is that they won after 21 days of racing. Occasionally we've seen a win after fewer, such as the cancellation of the original Val Martello stage in 2013 (so Nibali won the Giro in only 20), but generally speaking, it's a three week race which is occasionally slightly abridged in part, but has a genuine finish. If they just stop mid-race and they don't make it to the Champs Elysées, or the Paseo del Prado, or whatever, it won't feel right. With the abbreviated stages in the past, it all kind of came out in the wash. Bernal was still wearing the maillot jaune on the Champs and Nairito still crossed the line in Trieste in pink. Whatever happened in the middle, there was an ending, which gave a sense of closure to the race. It was over, and that individual had won it. I don't know if I would be able to have the same sense of acceptance of the winner if the race simply stopped after 15 stages and that was that.