It depends on how you set up your packages and targets. Reports are generated on the account where the package is hosted, as well as on the accounts of the targets assigned to the package. If you are using local ad packages (both package/s and target/s are on the same business account) and you do this on multiple business accounts under your enterprise, then you will indeed need to login to each business account to generate the report. To make a centralized report generation, you have to use a single business account (let's call this Account 0) where you create your packages, then assign targets/stations to it across business accounts. This way, you only login to Account 0 and generate the report, and you can choose for the report generated to be by target.