How is it finding subdirectories where subdomains are?

[big69]

I used xml-sitemaps.com free generator to make a site map of a maindomain.  It finds the directories where my subdomains are and it included all those files in the sitemap. I'd rather not have it do that.  How did xml-sitemaps.com generator even find these subdirectories if I do not currently have any url links within my maindomain to them?  I do have links to my subdomains but the current links to these are by linking them with their subdomain names.   I'd rather it didn't find these subdirectories because I'll make sitemaps of the subdomains separately.

Thanks in advance.

[XML-Sitemaps Support]

Hello,

you can exclude those subfolders from crawling using robots.txt file.

[big69]

Okay, Thanks!  That seems simple enough.   While searching I found this: 
[external links are visible to admins only]

Is there any true about google has done what is described there with subdomains?   

Thanks again.