Unable to get 1P to prompt with login data using Safari for a saved login

I have a 1P login item saved for website: https://delayrepay.tfwrail.wales/
In truth the login item was created for a related website: https://www.buytickets.tfwrail.wales/
but I added the second url to my login item. I have done this many times in the past: for example, my Apple.com login item contains 5 different urls and all of them work

The website: https://delayrepay.tfwrail.wales/ requires an email address to be entered, then re-entered

Using Safari I have tried two methods of completing this web form:

iPhone SE
iOS 15.2 (19C5044b)
Settings>Passwords>AutoFillPasswords=Off
Settings>Safari>Extensions>1Password=On

iPad mini (5th gen)
iPadOS 15.2 (19C5044b)
Settings>Passwords>AutoFillPasswords=On
Settings>Passwords>AutoFillPasswords>Allow filling from=1Password ONLY
Settings>Safari>Extensions>1Password=Off

In neither case does Safari / 1Password offer the login details for me to access the saved email address

From within the 1Password app (7.9.3 on the iPad) using the 1Password Browser, opening the website and tapping the key symbol, the login details are provided!

This has confused me. I have been using 1P on macOS since v4, and on iOS since when it was launched. I can’t recall a similar issue

I have come up with a workaround to the specific issue. I am looking forward to some explanation I can make sense of

Thank you, Andrew

1Password Version: 7.9.3
Extension Version: Not Provided
OS Version: iOS 15.2 (19C5044b)