I'm overthinking here, but the browser is essentially a JIT typesetter and job press inside a box of menus and buttons to control it.

For the "browser as publisher" question, what percentage of people know what an offset press versus letterpress is, or if talking about rendering, a Linotype versus Scitex? Even though you can touch the difference on a page, most people don't care. (Btw, does anyone have a working daisywheel printer I could buy?)

For the box of menus and buttons, thinking "browser as UI", what percentage of users know who makes their car radio?

The car radio is somewhat similar since some models have knobs, some have buttons, they generally tune in stations mostly as well as each other (except for one or two that pull in almost nothing). The car radio comes with the car, and can be replaced, but few people actually bother.

And if the radio's too specific, you could stop quite a few people on the street and ask them what kind of car (operating system) they have, and some will tell you, "A red one."