Yogasūtra I.46 - tā eva sabījaḥ samādhiḥ

All these [processes that involve an object of inquiry] are called Sabīja-samādhi.

These four levels are called Sabīja-samādhi, because they need a focus. They also involve preparation, gradual progression and sustained focus, otherwise, there will be distraction. Without preparation, there can be no foundation, and without gradual progression, sustained focus is almost impossible.