[gingerlime]

according to wikipedia[1]:

"Bounce rate (sometimes confused with exit rate) is an Internet marketing term used in web traffic analysis. It represents the percentage of visitors who enter the site and "bounce" (leave the site) rather than continue viewing other pages within the same site."

If the wikipedia article represents the true meaning of bounce, then GA is (technically) correct. It's not about reading/not reading, but only about going to a different page. If a user does not view any other page within the same site, even if they stayed for 2 hours and have read the whole thing twice, then they still 'bounced'.

That said, I still agree with you that conceptually, you might want to measure engagement. And bounce == no engagement made (in this context). However this is a bit more difficult to measure. Even if someone stayed for 20 minutes and scrolled past a certain point, it does not necessarily mean they have read the content. It is a closer approximation perhaps.

[1]https://en.wikipedia.org/wiki/Bounce_rate