I think it's a potential trap, unintended, but people follow the LGB "rules" and then go buy longer cars and then the cars sideswipe.
I find a track to track spacing of a bit over 9" is needed to keep the longest cars from hitting each other, but of course this is 1:29 and 80 foot cars.
I built my layout with clearances for 1:20.3 in terms of height and width... mostly large Mikados are the issue, very few long cars in narrow gauge...
On the 1:29 side, long container cars were the toughest, but I did not try the super long USA Trains auto carriers... they barely make a 10' diameter curve.
Greg