In 98-99 the NBA gave teams a short period where they were allowed to have 14 players on their active roster but that only lasted for a few weeks.
I remember up until the 2000-01 season, the Jazz would have a 12-man roster. If a player was injured, they'd sign someone to a 10-day contract but if #1-12 were healthy that would be the extent of their roster because Larry Miller didn't feel it was ethical to stash healthy players on the "injured list" - which is what it was called and required a medical-reason to put a player on it.
I don't think a 13-man active roster should continue beyond this year but it's a good move for this condensed season.