The Swiss squad has entered only one of its Gibson-engined R-13s at the Silverstone series opener on September 1, despite filing two entries for the series at the end of May.
No official comment was available from the team, but sources indicate that it has decided to run one car after suggesting that the chances of fielding a second were only 50/50 on the publication of the entry list.
It appears that last week's announcement by SMP Racing, its only real privateer rival in 2018/19, that it was quitting the series helped firm up Rebellion's decision.
It is understood, however, that Rebellion is looking at trying to run two cars at the Le Mans 24 Hours series finale next June.
Both Rebellions are due to take part in next week's official pre-season prologue test at Barcelona. Team regulars are expected to drive along with several newcomers.
It has not been confirmed who will race the solo car at Silverstone.
Only works drivers are listed against the two Team LNT Ginetta G60-LT-P1s for Silverstone.
Ginetta is still formulating its 2019/20 WEC campaign and hasn't ruled out its in-house LNT squad working with other another team or teams.
More names confirmed for Silverstone opener
Elsewhere on the 30-strong Silverstone entry list, ex-Formula 1 racer appears set to return to the Jota-run Jackie Chan DC Racing squad for the new season.
He is listed in the team's solo Oreca alongside after making two appearances with the team at the Sebring and Spa WEC rounds this year.
The addition of Stevens and Toyota youngster Kenta Yamashita at High Class Racing means all eight LMP2 cars entered for the season opener now have full line-ups.
In GTE Pro, only Ferrari is yet to finalise its roster for Silverstone, with Sam Bird not listed alongside regular co-driver Davide Rigon in the #71 488 GTE.
James Calado and Alessandro Pier Guidi are both set to return in the #51 car, while Aston Martin is also set to go into the new campaign with unchanged driver line-ups.
Aston factory driver .
Paul Dalla Lana's co-drivers in the #98 factory Am entry have yet to be determined.
Porsche young driver Matteo Cairoli has been reassigned from Dempsey-Proton Competition to Project 1 Racing, where he is set to join Egidio Perfetti and Davide Heinemeier Hansson.
Replacing Cairoli at Dempsey-Proton will be Austrian youngster Thomas Preining, who raced for another Porsche squad, Gulf Racing, last season.