do membership rules also hide posts from search engines?

I'm wondering if posts can be seen by search engines when I don't let my Strangers level see them... (I don't know enuf about how SEO works to know this.)

That is, in my selected Strangers Level, I only allow one Category to be seen (Public). I placed the Categories box into the Positive Rules area for that Level, and only the Public category is checked. This works fine, no problemo, my selected No-Access page comes up whenever someone clicks on any other post they might "see". Posts in the Public category come up fine.

I know I could insert a Read-More in any post, and as long as I've chosen them to be Protected by Default, then I get what I expect -- a click on ReadMore by a Stranger goes to the No-Access page. So, I could put a Read-More in every post, but I'm not keen on doing that for the 2600+ posts I already have in my db, and then I have to figure out how to do it for every new post, even automatic ones... ugh.

Can do, but do I have to?