Date archives with three-month name, not number

So, I’m having a bit of confusion. I used a custom function to be able to use %monthname% in my permalinks instead of %monthnum% and that works fine.

While poking around to find a way also to have my date-based archive pages use, say, Apr instead of 04, I noticed that for some reason right now, going to, say, /2023/Apr/05 will call up the date-based archive for April 5, 2023—which was a surprise to me. But, equally surprising given that, going to /2023/Apr/ does not bring up the date-based archive for April 2023. Instead it brings up the date-based archive for all of 2023.

So, wondering if anyone can help me understand a few things:

1. Why does monthname/date work?
2. Why does monthname not work?
3. How can I make this all work?

Note: I am under nginx, not Apache, so if any of the solutions involve rewriting things, I can’t use add_rewrite_rule.

Thanks!