In what way does it save time?

Not grandparent but it saves time the same way syntax highlighting saves time. You simply recognize the difference faster.

With http://example.com it's quicker to distinguish the protocol (http) and the domain name (example.com).

Compare that to http:example.com and it might take a bit longer at first glance (to some people), because they read over the : and then need to do a quick linear scan before they spot the : and are then able to distinguish http vs example.com

Given that one sees a lot of domain names, I'd say it'd save a few hours of everyone's life in the aggregate.

But humans rarely need to parse URL's into components but often need to read them aloud or type them. The extra characters make this slower and more error prone.

For most user interaction purposes the URL is just an opaque string. Only the browser need to actually parse the URL.

I don't think it's been common for most people to need to directly type or read URLs aloud for a long time.

The article is more than a decade old.

Should have been a ligature for it, instead of the actual ://.