Since the 2019-20 season stopped and then restarted, extensions using the 2019-20 season will be done up to March 12, 2020. This is because not all teams/players played when the NBA started back up.
On fantrax, you will need to change the option from 2019-20 regular season-YTD and instead change to 2019-20 regular season- Dates. Change the ending date to March 12 and then find out the players ranking for that season.