The short answer is lightspeed tracking doesn’t need anything extra to track a ship through hyperspace. As far as I’m aware, it created a static hyperspace map in a computer and was able to track ship movements through hyperspace by seeing changes in the map. Doesn’t make a lot of sense, especially when, as you have stated, there is already technology in-universe that lets you accomplish the same goal. But hey, it’s Rian Johnson, what do you expect?
The main difference is that with this computer, you can track any ship you want without the need of placing a homing beacon on it first, so you can track any number of ships you want whenever you want to. Also, some ships have scanners to check for things attached like homing beacons. This type of tracking would bypass that as well.
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