This is what OPs original question was about, you can’t always get a seat assignment at t-24, often times they are done gate assignment only, especially on fullish international flights, one of the many unknowns with a BE ticket, so yes if he is assigned a seat at t-24 it all gets easier, of course by the same token the better seats will also get assigned and be gone, I think OP is looking for clarity on what to expect as they have read various different answers, the unfortunate answer is that it varies and there is no way to know unless you work at delta and have more data than is publicly available