Yes, understood, and BPS works perfectly for each site. I am just trying to figure this out:
To put Server Account B primary.domain in Maintenance Mode in the way I am presently doing so, I have to copy index.html into the primarydomain folder since I cannot just leave it there all the time like I can at Server Account A.
The only thing that is different between public_html/.htaccess at Server Account A and Server Account B is that Server Account B's public_html/.htaccess file does *not* include this line:
AddHandler application/x-httpd-php53s .php
Is that why I cannot leave the "Maintenance Mode" index.html file in Server Account B's primarydomain folder all the time like I can at Server Account A?
Note: As far as I know, that AddHandler line applies to the entire account (all three domain) even though the following lines only point the primary URL.