No. It's the four best-ranked group winners.
"The qualifying group stage will feature twelve groups of four or five teams. The winner of each group will qualify for the World Cup, while the second-placed teams will advance to the play-offs, along with the four best-ranked group winners from the 2024–25 UEFA Nations League that finished outside the top two of their qualifying group."
They are the 14th best-ranked group winners. If 10 of the group winners ahead of them finish top 2 in the regular qualifiers then San Marino get a play off. You have to assume most/all group winners from League A and B will finish top 2. But it's highly unlikely that enough group winners from League C plus the other winner from League D will finish top 2. Most likely there will be no team from D in the play offs.