They really can have only 1, the 2nd may have only been brought forward to see whether it passes the completeness check. It will not be considered that year.
This is the approach they are following from quite some time. They Submitted Delhi/Mumbai at one go, Similarly Jaipur/Ramappa in another go. By this, they can plan for one year in advance & reduce of incomplete submission.
Group of Monuments at Mandu had been submitted the year before, but I cannot find evidence for that either
The same was also said by the minister in the same speech. He told that 'in 2019' we had sent Mandu nomination for completeness check. It was found incomplete, hence we had sent back to state Government. not sure whether it is before Jan or After. But news article suggests its around Oct- Dec quarter of 2019.
Also I assume Sarnath has a similar fate that of Mandu.