Compartmentalized tanks can enable the carrying of different fluids, but is usually to minimize the sloshing of fluid from end to end when the truck stops or accelerates abruptly.

Clearly they should have used Whiskey to flush to sanitize against influenza. My Great Grandmother was a nurse during the Influenza Outbreak in Massachusetts. She was told by a Native American to put a drop of whiskey under her tongue before visiting patients with influenza and she wouldn't get it. She did and she didn't catch the influenza virus. Although I noticed, from photos from that era, she had an awfully wide grin.

Material science and manufacturing progressed like most other things. What might appear overkill was probably the result of higher safety factors for material that had less consistent strength properties.

It's funny how it took a while for it to dawn on builders to enclose the cabs on vehicles. I guess people were just used to being exposed to the weather in wagons and didn't expect anything more when the internal combustion mode of transport came along.

Looking at the sign pasted to the windshield, I started to wonder about the fluids this truck is carrying. Looks like the tank's got three compartments ... maybe the front is O, the middle is A, and the rear is B?

Look at the size of those rivets holding the tank together. Just a little overkill but things were all engineered with a larger margin for error built in back then.