That they were two different people was definitely proven by another military diploma published by Werner Eck and Andreas Pangerl in 2007, giving both his praenomen and gentilicium: "Titus Flavius".
[5] He still held this post in January 89 when Lucius Antonius Saturninus, governor of Germania Superior, revolted against the emperor Domitian.
The expert consensus is that for his loyalty at this critical moment Norbanus was rewarded with promotion to praetorian prefect, one of the three most prestigious offices an eques could aspire to.
[10] No positive confirmation of this post has been found, and there is little room to insert him into the list of governors of this province: based on the work of Guido Bastianini, there is a possible gap around the year 90 when there are no precisely dated documents attesting to either Marcus Mettius Rufus or Titus Petronius Secundus in office, and a more substantial gap of precisely dated documents in 93 between Secundus and Marcus Junius Rufus.
What is clear, in Ronald Syme's words, is that "Norbanus slips out of historical record, and now, in October 97, a new commander, Casperius Aelianus, exploits the trouble".