From their white paper linked in the same comment > Provisioning To minimize the risk of data exposure, Slack adheres to the principles of least privilege and

From their white paper linked in the same comment > Provisioning To minimize the risk of data exposure, Slack adheres to the principles of least privilege and role-based permissions when provisioning access—workers are only authorized to access data that they reasonably must handle in order to fulfill their current job responsibilities. All production access is reviewed at least quarterly. so... seems like they very clearly can.