How equipment is unlocked

Okay so idk if its just my ocd and adhd heavily effecting me more than it should, but how exactly is the thruster acquired ? If you watched the 5 minute gameplay video ign posted a while back today, you’ll notice that chief acquires the thrusters via a spartan core. He doesn’t actually acquire the thruster itself, from what we know, im pretty sure some of the spartan cores allow the spartans to use certain equipment and others are used to upgrade those equipment within the armors diagnostics, so when he picks up this spartan core it allows him to use the thruster, and that makes sense, what doesn’t make sense is how does this apply to the other equipment, does it apply to the grapple shot too? What about the threat sensor, or the drop wall, the only other acceptable equipment is the shield core, ik its not something i should worry about but my ocd and adhd determine that, and right now those factors are causing me to overthink on it, what do you guys think