Can't remove app URL bar in TWA Progressive Web App for domains besides start page

[Android Central Question]

Hello,
NOTE: due to posting restrictions, I have replaced 'https://' below with ** (double asterisk)

I have created a TWA Progressive Web App directly by the guide on this google page: **developers.google.com/web/updates/2019/02/using-twa
And have added both the asset statements in the app and the assetlinks.json on my two domains exactly as described on google's sites.
When opening the app, there is no displayed app URL bar, however, if I click on a link to go to my second domain, the URL bar appears.

How do I make the URL bar remain hidden while navigating between my two domains?

Thank you,
Edward

Here are my assetlinks.json under /.well-known/ on the domains and asset_statements in the app ---
assetlinks.json:
[{
"relation": ["delegate_permission/common.handle_all_urls"],
"target": {
"namespace": "android_app",
"package_name": "com.exdomain.exsub.app",
"sha256_cert_fingerprints": ["59:81:22C:B0:16:95:A4:2D:F3:47:16:2A:9D:F6:63:E02:99D:36:ED:9C:ED:6B:C6:39:4A:89:E3:E9:24"]
}
}]

app asset_statements:
[{
\"relation\": [\"delegate_permission/common.handle_all_urls\"],
\"target\": {
\"namespace\": \"web\",
\"site\": \"**first.exsub.exdomain.com\"
}
},
{
\"relation\": [\"delegate_permission/common.handle_all_urls\"],
\"target\": {
\"namespace\": \"web\",
\"site\": \"**second.exsub.exdomain.com\"
}
}]

 

[B. Diddy]

I moved this to the Software Development forum for more specific traffic.