A screenshot of the page linked from the post this one is replying to, in portrait orientation. It's main heading says "Meta viewport test". Beneath that it says "This page has .", gives an option to" "Test initial-scale=1 instead", and then has a whole lot of "A long paragraph. A long paragraph." over and over again to make, you guessed it, a paragraph that is quite long. The layout looks completely normal and unsurprising.

The same page from the previous image, scrolled all the way to the bottom of the page. It just shows the bottom of the long paragraph.

The same page again, now in landscape orientation. This is the top of the page again, showing the heading and the meta viewport information. Again, the layout is what one would expect; specifically, the text flows all the way across the screen before wrapping to the next line.

You will no doubt be shocked to learn that this image shows the test page in landscape orientation, scrolled all the way to the bottom, revealing nothing but the end of the long paragraph (i.e., the text "A long paragraph" repeated over and over again).

Firefox portrait view, the paragraph shows three full sentences in width.

Firefox landscape view, the paragraph shows 6½ sentences in width, with 2½ wrapping to a new line, and then a more then half-screen gap before it wraps again to start over.