Ascenders and descenders rarely visually match on typical glyphs, so, no, perfect symmetry is usually not achievable

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But we appear to be talking in circles, so, please simply post a screenshot and your current settings, and we'll just whip up the GIMP's ruler to see that there's just 1px missing to fit a line or something

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(As an example, with a 0 bottom margin, you should expect the descender of a `g` to actually hit the last row of pixels, assuming the combined blackbox for the final line fits. [Also, that CSS doesn't screw the pooch? c.f., widows & orphans]).
EDIT: c.f.,
this issue for more details.