Players not able to join already going on public games

I’ve done some testing, and here’s what I observed:

If I join a public game simultaneously with my alt account (which is not on my friend’s list), we get placed in the same match. If my alt account joins about a minute after I created the match, it can still enter. However, after 3–5 minutes, joining that public game is no longer possible.

What I want is for public games to remain joinable even hours later, as long as there are still players in the match.

Has anyone else experienced this issue? If so, how did you resolve it?

Screenshot of the Island settings, let me know if you need anything else: