If I understand your query correctly, I think you need to be aware that, although quite a lot of journals do ask authors to nominate reviewers (both whom they do want and sometimes those whom they definitely do not want as reviewers), other journals do not do this, relying on their own chosen reviewers. In any case, I suspect that even when reviewers are nominated they are not used, either because the journal does not ask them to serve as reviewers or because they decline the invitation.
I hope I have responded appropriately to your concern.