I love statements like that, since the human eye cannot discern at 3 ft a 1 or 2 inch difference. I would bet if a set was on a layout and you did not know the manufacturer you could not tell what size the cars are? That’s the 4 foot rule, if it looks good at 4 feet it’s good. 😊
PENNCENTRALSHOPS
It's a matter of proportion. The height to length ratio is easily distinguishable to the trained eye. Most modelers can see the difference of an 18" Superliner from across a room as the length has been shortened, but the height and the width have not. The Lionel Amfleet cars are a different story as the height and cross section has been scaled down to match the reduced length of 19". They look scale because the X, Y, & Z planes are all scaled relative to each other. Of course, then pair those cars with a 1:48 scaled locomotive like the F40PH and it is easier to see that they are not 1:48 scale cars.
I'm an architect so being visual and seeing detail has been part of my daily work for over 30 years. When I was about 20 years old my father rebuilt the kitchen in the house I grew up in and I made a comment that the soffit above the cabinets wasn't even with the ceiling line. He told me it was. I got a tape measure out and it was off by 1/2" over 14 feet. He wasn't happy with me, but it was pretty clear to my eye. Having modeled passenger trains since age 12 originally in HO scale and later N scale before I discovered scale O, I quickly noticed that the Athearn streamlined cars I had were off compared to the real trains that ran by my house. This is not a new thing for me.
Of course, I have an unfair advantage with all of the cars in the title of this thread. I've been looking at scale drawings of some of these cars for close to five years and spent hundreds of hours checking, marking up, and rechecking PDF, CAD, and 3D computer models while creating all the master graphics for all the cars.
I'm happy you are pleased with your Lionel cars. We all enjoy the hobby differently and there is no right or wrong. However, you will find that most GGD customers look for the scale accuracy these cars provide because they can see the difference too. That doesn't mean they are right and you are wrong, it just means they have slightly different interests in this very broad tent hobby.