It's not without it's problems but it's a useful way of tackling the question.

I'd be interested in a few more details about your study if you'd like to provide them, I'm not quite sure what you found...

You used these contentiously loaded categories: 'reflective & complex' music apparently in opposition to 'intense & rebellious' music.

So CLEARLY intense rebellious music is neither reflective nor complex. Also, it conversely suggests that reflective and complex music may not be rebellious and intense.

This is the inference here.

'Reflective and complex' adults, and 'intense and rebellious' young whippersnappers are the findings of the study.

This judgemental categorisation isn't surprising as the categories for the study specifically filtered out music from artists that crossed creative boundaries. “In instances in which the appropriate genre of a song could not be determined by these means, the song was not included in the analyses.”
So artists that aren't creatively satisfied with a particular musical pigeon-hole, and expand beyond multiple genre's aren't represented. This is important because the most creative and insightful musicians are likely to be in this group, as most music fans will attest.

It should be noted how diverse the space is for music that younger people listen to. Young people are very familiar with obtaining music online for free (or very little cost), with all the diversity that the internet may provide – I'd hypothesise: it provides far more potential for diversity than even 50 years of experience of an average person's exposure to media may provide. Older people are much more familiar with buying in major label supported stores in brick-and-mortar shops. Further still, research suggests that people can have preferences for music styles set into them from when they are young, so it's possible the range of diversity they are willing to expose themselves to is set at an earlier age.

I would propose that music that older people have been exposed to will stick with them due to several factors, including limited range and exploration.
Could it be that older people have (disgruntly), come to accept inadequacies of their environment, while establishing themselves in the world of work, pragmatically, and slowly having their objections to the world's state of affairs, blocked out and die down along with unmet ambitions of their younger selves?

Expectations for them to calm down and 'act their age' steadily, and progressively rise. They become 'institutionalised', as in socialised into thinking like the organisations that they work at. Even if individuals don't settle down as much as social norms dictate that they 'should', record labels will very precisely target them with exactly what they expect they should like, as that 'older age group'. Simulacra and simulation – art reflecting life and life reflecting art, the puzzle of origin.

It sounds like you have found a correlation caused by differences in how people growing up are exposed to different kinds of music and sociological contexts. Of course, it's the old story: the Grand Narratives are gone and so as you say teenagers are 'clearly' "'trying on' different types of music for size".

But what if those young whippersnapper's aren't just enraged teenagers, pepped up on adolescences hormones, being torn between one self-identity and another?

What if they are on to something? Even if they are wrong, what if they are on to something?

What if this war waging, post-modern, advertising entrenched, individualist, corporate, Prozac saturated, industrialist society, isn't just fine?
What if, in part the positions younger people hold in society make them more able to rethink relationships between things before they become *part* of those relationships and then blind to them?

I've previously conducted a small study between young people's personality traits and how independent the music artists they like are.

It found that there is indeed a correlation between young people's tastes and the independence of their music label.
Inferring that corporate influence in music taste isn't easy to ignore, and that a more detailed study clustering the associations may more closely enlighten us to just how personality and music categories are related.