Of course Sofascore is better in stats than Whoscored and Transfermarkt but both of them have the same stats regarding Sancho.....funny that you claim that the the facts are wrong because journalist do not correct them. If he never played on the left how come he has 17 goals and 13 assists from the RW combinded for the 18/19 and 19/20 seasons compaired to 7 goals and 15 assists from the LW?
The videos aren't available in Germany. Anyway, he primarily played on the right side in the 18/19 season - that's his first season as a starter. 19/20 was pretty even with a slight preference of the left wing so it is only logical that he got more scorers from the right from 18 - 20 - after all he spent more time on RW in that time frame. But if we're talking about 19 - 21 it's a totally different story and if we consider his whole time at Dortmund it becomes even clearer since in 17/18 he was played almost exclusively on the left, too. 18-20 is pretty much the only timeframe spanning more than a season you could pick for your argument.
Moreover, you also have to look at the minutes he played. If you do, you actually see that his scorers per minute become better the more he played on the left.
20/21: Dortmund with a terrible start to the season; primarily on the left; goal or assist every 103 minutes. Only in the second half of the season: Goal or assist every 69 minutes.
19/20: Slightly more on the left than on the right, goal or assist every 67 minutes
18/19: First season as full starter, primarily on the right, goal or assist every 82 minutes
17/18: Debut season, almost exclusvely on the left, goal or assist every 137 minutes
As I said: I'm not making this up. I saw the majority of Sancho's games for Dortmund and he was clearly better on the left. I actually don't like just going by goal and assist stats since there is much more intangible stuff to all this (and Sancho is much better in the build up when played on the left side) but in this case it even shows in the productivity alone.