As an Administrator of the SonarQube Enterprise Edition v 8.9.6 instance, when I filter by Background Task type “Recomputation”, I am seeing the same “Recomputation” label description for both Projects and Portfolios.
Make sure you upgrade to SonarQube v9.9 LTS soon, not only to benefit from our Best LTS Ever™, but because soon we will systematically ask users to upgrade when they ask questions about earlier versions of SonarQube, which are now considered unsupported.