Sir, seems some wrong impression is there.
This Jan Shatabdi is fruit of discontinuation of Duronto only.
Before Duronto, there was no Jan Shatabdi.
On Railways being failed in getting optimum passengers for Duronto (as this much load is not there for Ajmer - Nizamuddin direct at a single service that too having just one ACCH & having no sleeping berths, may...
more... it be a day runner), they decided to discontinue Duronto and convert it to Jan Shatabdi halting at intermediate stations & thus taking passengers for / from there.
And this special service is as the Jan Shatabdi is still being run only twice a week while load is there.
Hope, this clears you.
Thanks!