Не разбираясь в таких тонкостях, сошлюсь на rtfm.
В описании CREATE TABLE - storage_clause
Цитата: The storage_clause is interpreted differently for locally managed tablespaces. For locally managed tablespaces, Oracle Database uses INITIAL, NEXT, PCTINCREASE, and MINEXTENTS to compute how many extents are allocated when the object is first created. After object creation, these parameters are ignored. For more information, see CREATE TABLESPACE.