Bokmål and Nynorsk are both systems designed as a common form of writing. None of them were ever meant to be a spoken language - they are "best effort" of trying to make a unified way of writing. That doesn't mean that it's not possible to "speak" them, as in e.g. reading aloud (though the intonation and pronunciation may still wary wildly depending on the speaker's actual dialect).

That means I was wrong in my original understanding!

> If they were solely written languages then you wouldn’t be able to, for example, read the text aloud, right?

I believe /u/Tor3's point is that Norwegians would read and pronounce nynorsk and bokmål the same regardless of the differences in the writing.

> Isn’t it similar to English in this sense?

It is. I don't pronounce English words differently when they're written with e.g. British or American spellings.