I think since 20966 intercity express starts from BVC at 6 in morning and reaches SBIB at 10.30 and 19031 Yoga departs ADI at 10.50 that's why Yoga is not extended till Bhavnagar because fir 2 trains ke BVC se departure/ arrival almost same time pe ho jayega so Yoga mostly BVC se ADI and ADI se BVC khali jayegi.
Instead a new bi weekly from BVC to Dehradun/ YNRK 1 day via Surendranagar gate and 1 day via SBT should be introduced.