Zooming basically changes the dimensions of the viewport as JS/CSS see it. Reapplying the zoom level would involve running the same CSS media queries and/or JS so that the website looks good at those dimensions.
It's not just an "optical" zoom.
But more directly, zooming can put you in very nonstandard width x height dimensions. Carrying those dims across different pages makes for an easy fingerprint which is probably why it's reset.
It's not just an "optical" zoom.
But more directly, zooming can put you in very nonstandard width x height dimensions. Carrying those dims across different pages makes for an easy fingerprint which is probably why it's reset.