No actually, they don't. Visible
posterization occurs when there are enough adjacent pixels with the same hue, saturation, and value (HSV) that you can see them as a "flat" region in the print.
The histogram only shows numbers of pixels with certain values (per channel if you are in RGB). What it does not do is indicate where these pixels are, in particular where they are in relation to each other. And it's the pixels' proximity to other pixels of the same HSV that defines posterization.
You may or may not have visible posterization after your adjustments. The only way to tell is to make a print and examine it.
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