Jesse;
"Good shot!" You are, of course, right about the notion that cloth (suits and uniforms) will not always reflect light to the same degree as the paint on the vehicle.
How I love the debates about photo-interp!
Your picture does provide a wealth of discussion of this issue.... things I would point out include the shading and shadow effects across that gent - proviso his suit is (was) indeed black and not some other dark gray or charcoal or..., the "black" tinted windows on the (LR?) behind him, the cool shading gradients on the car in fore-ground, etc. LOTS of cool things!
The car is, I think, revelatory... note that the shaded portions do indeed grade pretty close to black. Looking at the tank pic, you'll note that this does not appear anywheres near similar- even the clearly-shaded wheels and various angled plates appear in moderate grays - only the really deep-shaded under-fender / behind wheels appears pretty near black. One reasonable interp would be that the tank colors are simply lighter... others could include light-source angle, vehicle finish, etc.
The gent in the suit....! IF he's wearing "black", he may simply not absorb light to anywhere near the degree that those panzer guys do... maybe the "suit" is a glossier fabric. To me, I would never have ID'd him as wearing a black suit - way lighter all over, and clearly reflective in gradient, compared to those tinted windows behind him. The panzer guys, by contrast, exhibit very little shade-gradient and almost no "haiku reflectivity" on the upper-most lighted portions.
It appears that neither pic was taken in brilliant sun-light, which helps us here... Still, when all this is considered, this showcases why this lovely old debate continues! Each of us will arrive at the (argument) scene with our particular understandings of light, angle, reflection, color, etc., and each of us will arrive at our particular opinions and conclusions!
Me? I'll still maintain that the tank is NOT nearly black nor even very dark in color. And the color contrast of brown and gray is clearly evident. But that's only me!
"Viva la difference", or something like!
Cheers!
Bob