.htaccess allows access in one directory, but not another

[Loundry]

Background:

1. I have two separate Virtual servers set up, let's call them exampleA.net and exampleB.net

2. Webalizer dumps stats for these two virtual servers, repectively, into exampleA.net/stats and exampleB.net/stats. (That's the URL, from the filesystem it's /var/domains/exampleA.net/htdocs/stats, and similiarly for exampleB.net)

3. I have .htaccess files in both /stats directories which points to /var/domains/exampleA.net/.htpasswd (and similarly for exampleB.net)

Here is the behavior:

1. Connect to exampleA.net/stats, login with correct username / password. Success

2. Connect to exampleB.net/stats, login with correct username / password. Forbidden

3. Connect to exampleB.net/stats/index.html with correct username / password. Success

I can see that apache redirects exampleB.net/stats to exampleB.net/stats/ (with trailing slash) before it gives a 403 error (Forbidden).

Can someone explain to be why in the case of exampleB.net, the DirectoryIndex (index.html) is NOT being served? Perhaps can you also explain why this is NOT an issue in exampleA.net?

Thank you!