Hot take: Websites or publishing platforms including estimated reading time in blog posts is ableist. It says, "We estimate that a normal person reads at this speed, and if you don't, we're going to remind you at the top of every post that you're not normal."
For users who need or want an estimate of reading time, their user agent (e.g. the browser or a browser extension) should do that, in a way that's tailored to them.
Yes, my own open-source project's website currently has this (mis)feature. We got it automatically as part of the theme we chose. But I'm planning to get rid of it now that I've thought about it.