[Question] Patterns and Fossils

[notoyday]

I have covered my town in patterns and left a small space open for fossils to spawn, however I am not getting any fossil spawns. I assumed that the fossils would all spawn in the uncovered area but that doesn't seem to be the case

This FAQ has some discussion about it

Q: How often can I find fossils?
A: On average, you can find three fossils in your town per day. However, if your town is overrun with weeds or covered with patterns, this leaves less stops for a fossil to be underground (a fossil can't be under rocks, where a flower or tree is, etc.) and you may not find some or any that day.

Seeming to suggest that the fossils don't just simply choose whatever tiles are available, but maybe just decide to not spawn at all? Which kind of makes sense, as when I have had unmaintained towns in the past (without any pattern coverings), there have been a bunch of fossils, but at some point the spawns seem to plateau, and that's with the map only partially covered by existing fossils/weeds/etc, let alone the whole map with patterns

Has anyone ever tested this out or know how it works?

Thank you