No. One of the main benefits of backup is the ability to restore files which are no longer present on your computer. If you unchecked a folder in your selections list, the previous backups wouldn't be touched.

If you want to remove something from your backup sets, remove them from your selections (Selections > Regular Backup) and then use the "Total Reset" feature on the Maintenance tab to archive your current backups and perform a new Initial Backup- excluding the files you deselected.

Please consider that if your new selection size is more than 30GB, an Initial Backup to Disk might be necessary.