NASCAR teams in the modern era ( I am using 90's to current as modern) would clear coat over all the decals for the Daytona and Tallegeda races, Ive heard teams clear coating over wraps too( for those two tracks) that is really only the time it happens.
I see both sides of the table it and both have good reason for/against, yes, I clear coat over the decals on a lot of my NASCAR builds, and I have no cares to give if its not 100% accurate, some of the decals that are out there, need to be coated as they are not at all durable, like ALPS printed , Ive rubbed ALPS printed decals off from basic handling during the building, so yeah, protecting them is a thing.