It does mention a hope for long-term durable immune response, but the point about being able to pre-emptively roll out a universal vaccine is probably more important. This would lower the total rate of infections by a lot and allow people to reliably get a useful vaccine without waiting to see which strains are dominant that year. (Also, an immune response doesn't mean complete immunity. mRNA Covid vaccines don't prevent you from getting Covid. It lowers the severity and spread.)