I checked through the train list and found the first train, 09268 PRYG-ADI express which has start date missing. The news section of the same train indicated that it started running post 25th March, as there are articles on 24th March saying that this train will be introduced by 25th. As expected, in many of the trains start date is missing because no one updated it.
See, generally on this site, we don't indicate start date on train list. There is a dedicated area on train page, called Inaugral date where it is shown. The reason is that the inaugural date of many trains, especially pre independence era ones is still shrouded in mystery and requires a fair bit of investigation...
more... and poring over ancient timetables, old railway budgets, presidency Gazette of British and what not. Start date is indicated only for special trains as they run for set duration, and then stop running; normal trains are inaugurated once and continue running almost in perpetuity.
Currently due to the covid situation this mess has ocured involving special trains running as regular.
None of the special train will have start date earlier than may 2020, as that is when post the national lockdown first non-shramik all reserved special train started operations.