Chaser sheets is a private, internal tool. Once a day it writes a customer-service team's own work lists (which support tickets are waiting for a reply) into Google Sheets, so the team can see the full list behind a short daily summary.
It is not a public product, and nobody outside that team signs in to it.
It asks Google for one permission only: to create and manage the spreadsheets it makes itself (drive.file). It cannot see any other file in the Google Drive it writes to.