Read section "Where is the data stored and who has access to it?"

All data is stored on phone only, till the point someone is marked as Covid+. Then only the beacon tokens are uploaded to a central whitelist, wherein every phone can download and verify if they came in contact. In case of the contact data only for that day is shared.

Primary difference govt. can know only limited data of people who are +ve or came in contact not a perpetual continuous tracking of every mobile.