S3 1. tms-ci, etn mecullib: b is a h30 2. me me (a) (b) fo me htlkkne me me me me oh (c) =o (d) me

why here not more substituted alkene us formed as net3 attacks on more substituted hydrogen but here it is not why?? i know the mechanism how to solve it but I don't know why here less substituted hydrogen is taken by net3 though it attacks on more substituted one????