Sorry if Ask HN is not the right prefix?
I think part or what bothers me is the idea that you can assign a read time to something. Reminds be a bit of the part in Snow Crash where YT's mom is judged by how long she takes to read government memos.
I've added a (rough) word count to my blog posts' titles. That gives an indication of length without be prescriptive.
Of course, it doesn't include how long it takes to understand a diagram or watch an inline video.