Bob has a long history of honoring his friends who have passed, both publicly and privately, and I imagine at some point he will find a way that suits him to honor Levon, possibly beyond that statement, if he wishes.
He was there for many friends who passed on including Allen Ginsburg, George Harrison, he was there very eloquently when Warren Zevon was in his final illness. He was there, according to Eric Clapton, when Clapton's child died. I saw him play a song in concert in honor of Carl Perkins the day that Perkins' death became public.
It's his business whether he wants to do these things publicly or privately. Levon Helm was a life long friend to him and I don't think Bob should be judged by any public standards some would like to set for him as far as how he deals with losing people close to him. He made a public statement. Whatever he chooses to do now is his private business. He owes us no further display about how he feels about the death of Levon Helm. We need to get past wanting Bob to live his life in public. We have no right to expect it and he is free to do what he wants in handling his personal sadness about this. The last thing you need when someone dear to you dies is to have an audience waiting to see how you're going to respond and deciding whether you believe it was adequate or correct. Whatever Dylan is doing is what is right for him.
A lengthy public statement is not an indication of the measure of grief. Some people are naturally more private and deal with things in their own way and in their own time. I hope that it hasn't become a contest of who writes the longest tribute.