I'm fairly sure it was the caption for that photo, but possibly I saw an Erie ad touting their large clearances, implying overhead as well as lateral. I don't have my own copy of the book unfortunately. I'll have to see if my local library still has their copy and take a picture of the relevant page.
There are two EK - Erie related photos. One is on page 88 of 1 of 2 chemical storage tanks from Warren PA. They measured 16-8' high, 12-7' wide, and 16' long. Eire and EK men are pictured.
The second is page 90 and shows one of the wheels being delivered from Westinghouse to EK standing 18-6' above the rails (not a wheel car itself). It was the highest shipment ever over the Erie.
The text style is different from Gordon's book so I assume it's right from an Erie magazine or publicity photo.