I might disagree. I have no idea whether the rumor is true or not but I see him as one, who like many in the NFL,is very successful as a coordinator but not necessarily as HC.
He took over an offense that was less than mediocre and within 2 years had them at or near the top 10 in the nation in both scoring and yards for his entire tenure at OC, breaking records for yds, TDs Passing TDs scoring etc.
Remember where we are in the pecking order. Most people will either be making a horizontal movie or excel at a lower level to come here.