Hiyama vs Sonogashira coupling
So I will answer my question. In Organic Chemistry Portal it is written that Hiyama coulping requires an activating agent such as fluoride ion or a base because crucial for the success of the Hiyama Coupling is the polarization of the Si-C bond. Activation of the silane with base or fluoride ions (TASF, TBAF) leading to a pentavalent silicon compound is a first necessary step. The whole mechanism is given here:


On the other hand, Sonogashira coupling doesn't require any activation and it happens preferentially in the above mentioned synthesis.