The isocyanate silane is a small molecule with the -NCO group on one end and the -Si(OR)3 group on the other end. The -OH terminated polymer is dissolved in ethyl acetate that is
It is unlikely, usually silyl chlorides are needed to react with OH and even then you need some sort of active nitrogenous like pyridine, DMAP, or imidazole to form an activated silinium cation.
Plus the more bulky your R groups on the Si, the more unreactive it becomes.