Nothing necessarily precludes it but does it really happen that often? I couldn't find any data on this. Is there any evidence that "changing careers" is easier and more likely under the German VET system as opposed to the US system? In fact, evidence suggests that the permeability between the academic and vocational tracks is quite low in actuality [0]. One would logically think that making long "on the track" prerequisite chains a requirement for a career change would add significant barriers to entry. And there is some evidence that supports my theory that VET-like systems increase social stratification and socioeconomic inequity [1][2]
>They don't assign you a vocation.
A difference without a distinction IMO. They assign you a track of schooling which will leave you qualified for only a certain subset of jobs.
[0] https://www.oecd-ilibrary.org/education/a-skills-beyond-scho... page 38
[1]: https://link.springer.com/article/10.1186/s40461-016-0033-0
[2]: https://www.semanticscholar.org/paper/The-social-stratificat...