The phrase kallā bal rāna in Sūrat al-Muṭaffifīn also contains a reported sakt. The brief silence keeps bal and rāna distinct in recitation.
Uninterrupted assimilation of the l into r would miss the special mode.
The four familiar locations are in al-Kahf, Yā-Sīn, al-Qiyāmah, and al-Muṭaffifīn.