Every Islamic financial contract has its own principles and conditions. A transaction does not become valid merely because it is given an Islamic label.
A genuine cost-plus sale (مرابحة) must actually be a sale. A genuine leasing (إجارة) must actually involve usufruct of an asset. A genuine partnership (مشاركة) must actually involve partnership rights and risks.
The substance of the transaction matters more than its label.
This principle will be used repeatedly in later levels.