About the example at Wiki, maybe I interpret it wrongly, like this:
Si(Ph)C=CH(Ph) here Ph is on Si, which is impossible with tetravalent Si
SiC(Ph)=CH(Ph) here Ph is on C, the product I expect after Si-H adds on C≡C
What is the convention? (Branches) written always after the carrying atom, like in Smiles, would be unambiguous but bring here the drawback of separating the C from the =.