The largest majority of scrapers operate on cut-to-fill, on relatively level ground.
But I guess, if you were involved in fairly deep excavations with scrapers - then yes, you need to cut back on scraper size for serious uphill work.
It's been a long, long time since I've seen any scrapers - either pull or powered - used on hauling up steep slopes.
But way back when pull scrapers were all the rage, we used to construct large dams ("excavated earth tanks"), using dozers and pull scrapers.
However, even then, you mostly hauled the scraper up the corners of the excavation to reduce the climb angle.
This is a local 40,000yd dam, being built in 1960. The machines belonged to my brothers employer. Cable control ruled, in those bad old days!
The last photo was a levelling job for a big sports field.