Why is the organic compound $\ce{C6H5-CH=CH-CH2Cl}$ named 3-chloro-1-phenylprop-1-ene and not 9-chloronon-5,7-dien-1,3-yne even though there is no specification whatsoever that there is a phenyl group in the organic molecule? $$\ce{C6H5-CH=CH-CH2Cl}$$ can also be written as $$\ce{CH#C-C#C-CH=CH-CH=CH-CH2-Cl}$$ and the name for this organic compound would be 9-chloronon-5,7-dien-1,3-yne. How do we surely know that there exists a phenyl group in the molecule?
Also why is phenyl treated as a substituent and cannot be considered in the longest chain?