Segments using Referrer URL and Referrer Name

Hey all

I’ve been doing some work recently in creating segment across two of our subdomains (a.example.com, b.example.com).
I want to know when someone is moving between the two subdomains, so I created a couple of segments:

On a.example.com, I create a segment which has Referrer URL starts with https://b.example.com
On b.example.com, I create a segment which has Referrer URL starts with https://a.example.com

This doesn’t work: nothing shows up in the segment at all.

However, which I change the segments this:

On a.example.com, I create a segment which has Referrer Name b.example.com
On b.example.com, I create a segment which has Referrer Name a.example.com

This works and shows me the data I’m looking for.

In the documentation on segmentation values, I see:

I tried using the Referrer URL with a URL-encoded prefix (as shown in the doc) but this doesn’t work either.

Can anyone explain what Referrer URL and Name actually contain?

Is it possible to get the doc updated so that this is clear?

Thanks!