This kind of early access depends entirely on relationships, not on any special buyer status, so an agent who is actively working their network of other agents will surface these opportunities more often than one relying only on public search.
The tradeoff is that a pre-market home has not been fully priced against public comparables yet, so a buyer moving early should still confirm the asking number against 3 to 4 recently sold comparable homes before making an offer.
Ask your agent directly whether they have anything coming that matches what you want, since that question is what actually unlocks this kind of access. Get your hand-reviewed valuation from Joel Dyck.