I believe there may be a slight misinterpretation concerning tannins. Oak alternatives and powered tannins are 2 different things and serve different purposes. Alternatives add an oaky flavor to the wine and to some extent add tannins. Powered tannins are not always derived from oak. Their purpose is to help the aging process and improve wines that are somehow lacking. Finishing and cellaring tannins are used post fermentation and sometimes added a few week prior to bottling. Sacrificial tannins are added at fermentation.