Well it's just buying a bunch of accounts with different IPs.
Instead of buying from different hosts (which will naturally give you different IPs),
you just buy from one provider.

It's called "SEO" if your purpose is to use those accounts to build a network of sites of the same niche. So technically they look like different sites because they came from different hosts or IPs.

So its moreso about IP diversification?

Which I guess allows you to host your OWN sites under the one account, and they appear to the search engines as completely unrelated websites from different locations?

Would I be right in saying that?

You are right that's the idea behind it.