I am saying this according to site rules
🔹"Via Yeswantpur" is required only for Dadar - Tirunelveli - Dadar Express because there are two trains running in different routes but source (Dadar) and destination (Tirunelveli) stations are same. So "via _____" is required. Another train in between Dadar and Tirunelveli is 22629/22630
🔹"Via Yeswantpur" is not required for Dadar - Puducherry Express because this is the only train with source as Dadar and destination as Puducherry