There is no such thing as “candidate-elect”. Primaries have become the accepted way for parties to choose candidates, but there is no legal or constitutional requirement for them to do so. As a matter of fact, historically it is a relatively new phenomenon for the public to have a voice in selecting the candidates for president. Well into the 20th century, the “smoke filled room” was the way candidates were selected. There is no nominee for president for a party until the party designates one according to their own rules, regardless of how many people voted in primaries.
All of that is to say there is absolutely no issue with whomever the Dems select at the convention from being on the ballot in all states. If it is not Kamala, there is an issue with the money raised already for Biden, but that is another subject.
Sorry to say, but you are correct. Ds haven’t nominated anyone yet.