From what I gather, it looks like you're registering the web adaptors on the new machines to the portal and server in your primary site. Instead, you want to register them to the portal and server in your secondary site. In your first screenshot, the URL you reach the web adaptor registration page with should be the URL to your primary environment. However, since you have the etc\hosts entry on that machine, those requests should resolve to the standby web adaptor:
In the example above, my production/active system is accessed via enterprise.domain.com. The enterprise.domain.com machine has a web adaptor on it and the WA is registered to Portal and Server on m1.domain.com. These are all entries in DNS. I want to stand up a new environment to migrate to, so I'll:
1) Create the new machines. They end up with hostnames enterprise1.domain.com and m2.domain.com. enterprise1.domain.com has an IP address of 10.0.0.2.
2) In the etc\hosts files on each machine, i'll add a entry that resolves enterprise.domain.com to 10.0.0.2:
10.0.0.2 enterprise.domain.com.
Now on each of those machines, if I reach enterprise.domain.com, the request will resolve to the machine that has an actual FQDN of enterprise1.domain.com.
3) Install the web adaptors on enterprise1.domain.com.
4) Install Portal, Server, and Data Store on m2.esri.com and create the sites/register the data store
5) Register the web adaptor on enterprise1.domain.com to m2.domain.com via https://enterprise.domain.com/<wa context>/webadaptor/portal to portal and https://enterprise.domain.com/<wa context>/webadaptor/server to server. Again, these requests will be directed to enterprise1.domain.com
6) Federate
7) Run the DR restore
The approach described above minimizes downtime for your original environment. Another approach would be to:
1) Set up your new machines for only Portal, Server, and the Data Store, (m2.domain.com)
2) Register the web adaptors on enterprise.domain.com with the machines on m2.domain.com
3) Continue to set up the environment, (registering the ArcGIS Data Store and federating)
4) Run the DR tool to restore the backup
This will take down your production environment for a bit.
I'll take a look at the blog and make sure that our instructions are clear.