Backup incremental level 0; VS RECOVER COPY OF DATABASE

Hi guys,

as it written in Documentation, best practice is to schedule a daily incremental backup, and a weekly full backup.

RECOVER COPY OF DATABASE WITH TAG 'OSS';

BACKUP DEVICE TYPE DISK INCREMENTAL LEVEL 1 FOR RECOVER OF COPY WITH TAG 'OSS' DATABASE;

BACKUP DEVICE TYPE SBT ARCHIVELOG ALL;

BACKUP BACKUPSET ALL;

DELETE ARCHIVELOG ALL;

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the question is:

why do we need to do a weekly full backup, when we do "RECOVER COPY OF DATABASE WITH TAG 'OSS';" before each "INCREMENTAL LEVEL 1", is that doesn't mean .. that the old backup will be rolled forward to the last SCN, which means .. the old backup will be just like 'full backup' ? right ...