Like the others, I didn't see them as spools, at first glance.
Though with the explanation, they do come to mind as the old wooden spools.
Plus, thinking back, way back .... , there was a wooden spool that more chunky, and would be more like those proportions.
Something to think about ... there are so many different types of spools today, that I so seldom see this older style, even if re-proportioned. Maybe you would want to emulate Aurifil spools? There is a free pattern to make those, somewhere on the web.
I agree, the two close-coloured-tonals works well to emulate the thread.
Good Luck! ... and have fun with it.