In what way aren't they the same?
They both detect and store ID info of devices running the same app that you have been in close proximity to, this enables authorities to potentially notify the owners of those devices in the event of one of the owners of said devices testing positive for COVID ... and then only if said person decides to upload that data.
Obviously, you would install the app that has the greatest public presence in your region otherwise why bother?
Put it another way:
You install an app designed for Australia, (COVIDSafe), but you have close to zero chance of meeting an Australian due to the lockdown on international flights, then you'll never be notified of a near miss in case someone in Australia tests positive.
Conversely, in the meantime you might have been exposed to half a dozen locals with the infection but you'll still never get notified because while they were running an app for that region, you were running one for Australia.
These apps do not all talk to each other through some central database, nor are they likely to use the same protocols to communicate to each, you only have to look at the Wiki page I pointed to, there is ~12 different protocols.
BTW, where exactly does it say that TraceCovid uses the GPS?
Like most other similar apps, it uses Bluetooth to detect another device running the app within a distance of around 3m, (and sometimes if it's only within that distance for a minimum period of time).
No location info is collected because they can get that from info provided by Google/Apple/carrier and the phone itself, (if they're allowed).