Sub-domain for more secure MySQL host?


I have read a couple of posts on the forum here that suggest using a random string as a mysql host (rather than using
This makes sense to me, and I have started using this on new websites I set up.

Usually, when I am first setting up a website, I will use the subdomain to start with while I wait for DNS to propagate, or for my client to decide which domain they will use, etc.

I wonder then if it makes sense to just keep the sub-domain as the mysql host. For example: …not using the main domain at all as a mysql host, for even more obscurity

Can anyone think of reasons for or against this? Since the domains both point to the same place I would imagine there are no performance issues.