It lost me, because we have two estimations - an overall size guess of an epic and an actual implementation estimation of an epic. Like the overall size guess is just 2-3 seniors looking at an issue and wondering if this takes days, weeks, months or years to implement.
The actual implementation discussion is however what the article is talking about. We get most or all of the team into a meeting and we talk through what needs to be done, and structure all of that into individual concrete tasks everyone can have an idea of implementing them. And then we estimate those tasks.
And this estimation in turn is communication to management. Like, we've realized that about 21 is what one of us can do in a usual monthly iteration outside of massive outages and such (we're an operational team). So if an epic turns out to require some 3 21's and 3 13's... that can easily take 6-12 months unless we put exceptional focus on it. With high focus... as a team of 4-5, that will still take 3-6 months to do.
On the other hand, something that falls into a bunch of 5's and 9's and such tends to be muddled and struggled through regardless of whatever crap happens in the team much more reliably. It needs smaller chunks of overall attention to get done.
And note that this communication is not deadlines. This is more of a bottom-up estimation of how much more or less uninterrupted engineering time it takes to do something. A 21 in our place by now means that other teams have to explicitly make room for the assigned person to have enough headspace to do that. Throw two interruptions at them and that task won't happen.
It's more bin-packing than adding, tbh.