Fonts designed with incorrect gamma rendering also assume specific colors for foreground and background. With incorrect gamma the stems get thicker when rendered black on a white background, and thinner with inverse colors.

So even if a font is designed with incorrect gamma, it might still not be the best to render it with incorrect gamma, as you might use different background and foreground colors to the designer of the font.

AFAIK freetype has the option to enable "stem thickening" to consistently correct for incorrectly designed fonts regardless of colors being used for rendering.