Wait until you try http:/example.com and http://////example.com in your browser.

Your first example is a valid uri but not a valid http url, because it's missing a host part. Your second example is not a valid uri, as the spec requires that [scheme]:// is followed by a host indicator.

Neither has much to do with / normalization, which applies to the path part of a valid uri.

In both cases I get https://example.com/ in FF.