...Roots are covered.

Sometimes they graft higher in case of failure they can go lower? Maybe this is what is the case. Make sure that the graft union is 2-3" above ground, and as long as the roots are covered, you should be good. I know they need Zinc, so you should know if your soil has enough. Here's something cool.
http://leaderpub.com/2012/08/23/niles-woman-waits-15-years-for-first-pecan/
Noogy

As long as the roots are covered, I don't see a problem.

When planting from a container, is is customary to locate the root flair, which is often too deep in the container, and use that as your guide when gauging planting depth. If the root flair is covered, that is deep enough. Al

As an aside to show you are not too high.....researchers have developed a way to grow peach trees in ground that is infested with Armillaria root rot. They plant the tree still in a pot but with an open bottom so the roots go out and down in to the native soil. After a year they remove the pot and the soil and the tree looks like it is standing on legs which are the main roots which are out of the ground for several inches. The trees look like they are perched on legs. The theory is that the root rot when it goes uip a root and hits the sun shine will go no further thus saving the tree. Just show how adaptable plants are and that too high (within reason) is ok.