How so? LaForge's rank progressed smoothly, whereas Tuvok almost certainly had to have been demoted at some point.
I don't know when Jadzia underwent her symbiosis training, but it easily could've been in her late teens. There's nothing saying that a symbiont is awarded immediately after graduation, only that they're eligible after passing the tests. So Jadzia may have passed her symbiosis training, went to the Academy, then bonded with Dax, and had a posting before meeting Sisko again at DS9. It's murky, like Kirk's backstory.