Originally, GM placed the “L” and the “R” at the end of the shift quadrant to facilitate “rocking” your car out of snow, mud and sand by quickly moving between reverse and low. I’ve seen some Jam Dandy films on You Tube that demonstrate this, and I recall reading about this maneuver in old GM owners manuals.
When I was in HS, in 1966 the neighbors up the road from us had a 57’ Buick Station Wagon and also a 63’ Rambler Classic 4 dr. The Rambler had the PRNDL set up, while the Buick had PNDLR. Once, Diane, the middle daughter was following the school bus up a very step grade, and the bus driver Mrs. Denton always had to come to a complete stop at a certain very steep spot and shift into 1st gear. Well Diane, was used to driving the Rambler, and forgot that reverse was at the end of the quadrant in the Buick and slammed the shift lever of the Buick into reverse by mistake, thinking she was shifting to low and dropped the transmission right on the spot, with all of us laughing at her bad luck. Fortunately, her Dad had a tow truck too, and was able to tow the Buick back up the grade.
Eddie