Yes and no; I know that's vague so let me elaborate.
In the world of outreach, "list" has a negative connotation. Most people who sell outreach services use a form of "list" or "spreadsheet" or "database" in order to place you on blogs. Upon ordering from a number of different services you'll start to notice that it seems like they're all using the same blogs. This can be due to how they outreach and generate their lists, or they're reselling from the same provider. A visit to Globex Outreach
sort of paints that picture; Why is it that a service that sells guest posts is trusted by another service that sells guest posts? I'll let you read between the lines.
Over time we've curated a database and that database is absolutely used when placing you on sites. However, unlike other providers, we put extreme effort into pruning that database. The database is hooked via SEMRush APIs; Whenever a site loses large amounts of traffic (is possibly penalized) we look at what might of happened. Unlike your other providers, we know why a site might of tanked and what went wrong - these sites are subsequently blacklisted in our database. Did the site start having random links to casinos in their sidebar? What does their recent content look like? etc.
Meaning, yes, pre-existing relationships (a database) are used. However, fresh outreach is always being performed and new sites are always being added to the database; Sites that might of been in the database one month, might get retired the next.