Custom structure permalink preventing 404

I am trying to find out what impact setting a custom stucture prefix in permalinks has on 404’s

I have a custom structure of:

/news-opinion/%postname%/

This is working as expected if you tried to go to a page: domain.com/news-opinion/non-existing-url I will get a 404 as expected.

However if I use: domain.com/non-existing-url this will redirect a user back to the homepage and not 404.

Am I missing somthing here I should have accounted for?

This is a Bedrock / Composer based install and this is the list of plugins in use if any of these are known to cause this issue:

"wpackagist-plugin/cache-enabler": "^1.3.4", "wpackagist-plugin/classic-editor": "1.5", "wpackagist-plugin/relevanssi": "4.2.0", "wpackagist-plugin/safe-svg": "1.9.4", "wpackagist-plugin/wp-mail-smtp": "^1.8", "wpackagist-plugin/instant-images": "4.2.0", "wpackagist-plugin/shortpixel-image-optimiser": "4.16.1", "deliciousbrains-plugin/wp-migrate-db-pro": "^1.9", "humanmade/s3-uploads": "^2.1", "custom-repo/advanced-custom-fields-pro": "^5.7.0", "custom-repo/gravityforms": "^2.4.0", "wpackagist-plugin/duplicate-post": "3.2.4", "wpackagist-plugin/filebird": "2.7.1", "wpackagist-plugin/crop-thumbnails": "1.2.6", "wpackagist-plugin/redirection": "4.7.1", "wpackagist-plugin/advanced-cron-manager": "2.3.10", "wpackagist-plugin/wp-seopress": "3.8.4", "wpackagist-plugin/cookie-bar": "1.8.7", "custom-repo/vcaching": "^1.8.0",  "wpackagist-plugin/wordpress-importer": "0.7", "wpackagist-plugin/export-media-with-selected-content": "2.0", "wpackagist-plugin/user-roles-and-capabilities":"^1.2.3", "wpackagist-plugin/wp-all-export": "1.2.5" 

If I can provide any more information that may be pertanent to this please let me know.

Any help with this would be apperciated.