It is open. It was a hard ADR to get before, now with limited capacity it's even harder. I had a hard time getting one for a party of 3, but got one for a party of four. It's ok if less people show up, it's only a problem if more people show up than what's on the ADR.
SciFi is a hard one for sure!
Touringplans has a free reservation finder (you can search two ADRs at a time), that can help a lot, along with stalking WDW page since availability is immediate.
Book for 4 or 6. Due to current seating arrangements (one party per car), you won’t be stopping another family from getting a reservation. The system doesn’t recognize that and loads in almost all 4 or 6 size groups.