The SQL VSS service can be used for a number of things. Simply having VSS writer active will not in itself cause problems with your backup chain.

One typical use of VSS writer is with disk-based backup agents. You may find your Windows people have included your database in their backup plan. You may even find they are only sending offsite the backup they think they have made, or their DR plan is to only bring back onsite the backups they have made.

You should check with your Windows team if they have any tools that could have used VSS writer to take a backup, why they think they need to do them, and how the backups you take fit in to their DR plan.