I have a bang for Hacker News overriding the default !hn bang, with the intent of making it so searching "!hn" will bring me right to Hacker News. The default behavior is that it will bring you to https://hn.algolia.com/, and will use https://hn.algolia.com/?q=%s given a search term. The snap for @hn will correctly use site:news.ycombinator.com, so I often search "@hn !" to navigate to Hacker News.
I created the custom bang with the intent of making "!hn" navigate directly to https://news.ycombinator.com by using these settings:

But this behaved exactly the same as the default bang.
If the user enables "Open Base Path" when a value is set for "Domain for Snaps", it seems like the user would always want to navigate to that domain, instead of navigating to the bang domain for searching. If there is a different search domain than domain you want to use to search Kagi for content, the former seems like it would always be a specialized search site, and the latter would be the site of interest. Therefore "Open Base Path" should bring me to the site of interest: the Snap domain.