Hello all, I was taught to never join cables in trunking. Is this compliant?

Regulation 6.3.7.1: Joints and terminations of cables, cores and conductors shall be made in accordance with manufactures instructions or the appropriate part of SANS 10198. FLEXIBLE CABLES SHALL ONLY BE JOINED USING TERMINATION BOXES, CABLE COUPLERS OR MANUFACTURES JOINTING KITS.

My question is for the joining of a twin and earth cable using ferrules