I think you're onto something here. Looking at the comments by the media in the discussion today about how they've handled the Marius situation, they probably have stories that they're sitting on about everyone, not just Marius. If Haakon and MM got wind of this, they may have encouraged SV to bring the girlfriend, rather than having the media "out" them, like it's a scandal.
Based on the precedent with Princess Ingrid Alexandra (who receives even more interest from the media and public), it seems even the boldest of the media (i.e., Se og Hør) would wait until both parties were adults before "outing" them, and it would not be presented or received as a scandal.
If the goal had been to preempt potential reporting on the relationship after Amalie Giæver Macleod's 18th birthday in November, the public introduction would surely have been handled in a different way – perhaps a strategic leak to a friendly outlet with on-the-record confirmation from a spokesperson that the two were in a relationship but did not want to comment further, or perhaps giving permission to picture agencies to photograph the couple holding hands outside some non-royal social event such as Miss Macleod's 18th birthday party.
As it was, many elements of the introduction – Macleod walking not just next to her boyfriend but with the entire crown princely family set apart from the public, at a grand royal event which was of great public interest even though it was officially "private", at a time when three other members of the royal family were generating headlines and negative commentary on a daily basis, and wearing a dress reused from the Crown Princess's pre-wedding photoshoot – appeared designed to boost media and public interest, rather than tame it.
It would be unfair to arrive at any judgments about the Prince or his girlfriend based on just one public relations decision made when they are only 17 and 18 (assuming, as I do, that it was their decision though their parents must have agreed to it). However, because many have praised this introduction as good PR or argued that it bodes well for the couple's potential to represent the monarchy, I will counter by saying that
if the couple continue to make similar decisions over the years as they grow older, that would not be a positive sign for the royal house. It is good for royal "spares" and their partners to be comfortable with public attention, but spares and spouses/partners of spares who actively seek attention often have issues with their designated roles.
Besides, I hope that future King Haakon continues the gender-equal approach his father has so far taken, meaning that a possible wife of Prince Sverre Magnus should be treated no differently than Ari Behn or Durek Verrett, and not take on duties for the royal house unless there is no alternative.